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161 Posts
Discussion Starter · #1 ·
Just a general newbie question. Since we need phosphate anyways, why isn't anyone using phosphate based buffer? Isn't phosphate based buffer more stable than carbonated based buffer? The only negative that I could think of is that it'll invalidate the Co2/kh/ph relationship or that it may add too much phoshpate.

The problem i see with using baking soda or bi-carbonate is that it's highly unstable. If you have driftwood leaching tannins, your KH could easily drop to zero.

313 Posts
Because phosphate has been perpetuated as an algae growth accelerator. I would just keep using mono-potassium phosphate, because I kill 2 macros with one scoop instead, lol.

21,012 Posts
First, there is no reason to try to buffer the water with anything, except in rare cases, where some fish won't breed otherwise. When you add any salt to the water, whether it is a bicarbonate, carbonate, phosphate, or whatever, you are increasing the total dissolved solids in the water, and messing with the fishes osmotic balance (so I am told). So, ideally you add nothing to the water that isn't necessary. The amount of a phosphate buffer you would have to add to maintain the pH where ever you decide it should be would be far more than we ever add of any fertilizer. We add the order of 10 ppm or less of any of the fertilizers, but just one dKH is more than that of carbonate, so it would take more than that of a phosphate buffer for it to work too.

We should be concentrating on fertilizing the plants, feeding the fish, and keeping the water clean. Not on trying to hold the pH at some particular value.

161 Posts
Discussion Starter · #6 ·
Below is a really good article I've read about the GH/KH/Electrolytes in general. In the past, I've kept KH to near zero and my PH would be around 5.6. All the plants were doing fine but I do notice that my fish are more desease prone. So before slamming me, this is just based on my observation. Some of the rainbow fish had columnaris. Recently, I've up the KH to 3 degrees by using Seachem Alakaline Buffer and PH went up to 6.4, and them all of sudden, in matters of few days, the patchy white stuff on the skin went away (columnaris) and the fish seems to be doing much better and feeding better. The only change was KH, which I think indirectly improve the fish health by creating a higher PH range that they prefer. I don't know for sure if that's really the case or not but that's what I'm suspecting based on the article below


By Carl Strohmeyer
Updated 9/18/09


Many aquarists overlook the need for electrolytes, mineral cations such as calcium & magnesium and the effect of KH (Carbonate hardness) in their freshwater aquarium. Minerals such calcium are essential for osmotic function in fish and many aquarists make the mistake of believing that some fish such as Discus do not require Calcium or minerals when in reality these mineral cations are essential and GH test kits to not give the full picture (Important, please see the GH section for more). Fish will often adjust to poor electrolyte and calcium (& other necessary Redox reducing elements), however this does not prove this is best anymore than fish that adjust to aquariums that are crowded with infrequent water changes. As in aquariums that are overdue for a water change then finally have one, aquariums that are brought up to good mineral/electrolyte levels by use of products such mineral blocks or alkaline buffers such as Sea Chem Buffer may also show initial stress until the inhabitants adjust to the improved water quality.

Often aquarists in both fresh and saltwater worry too much about pH while ignoring the importance of GH and KH (alkalinity in SW) as to pH stability which is more important than the actual pH number in freshwater. In marine aquariums the actual pH number is of higher importance than in most FW aquariums, however even in saltwater a correct alkalinity (KH) is a must for proper buffering of marine pH and as well elements such as Calcium, Magnesium and Chloride are also very important to a healthy saltwater aquarium as you will read further in this article.

Popular aquarium traditions state that only certain fish need water high in electrolytes and calcium, this is only partly true. The Fish Body (organism) is alkaline by nature and is constantly attacked by free radicals which are usually acidic. While freshwater fish absorb needed H2O (saltwater drink constantly), the need for these electrolytes and calcium for some fish (such as Amazon River fish) is lower than some, however Proper Osmotic function stills requires that calcium and other electrolytes be present in the aquatic environment as well as foods. This is why I have found that even fish such as Ram Cichlids thrive in a Reducing environment that has a Calcium level that often brings the GH over 150 ppm and why the aquarium traditions of lower GH for certain fish are only half correct as they miss the aspect of balancing water with important mineral cations.

KH is basically the alkaline buffering capacity of your aquarium (there also is an opposite acid buffering process), a KH above 50 ppm helps prevent sudden drops in pH. KH (carbonate hardness) is an important source of energy for nitrifying bacteria that eliminate ammonia and nitrite. In addition, carbonates are used by plants for photosynthesis when carbon dioxide (CO2) is absent.
You can convert dH (German hardness) to ppm by multiplying your dH by 17.9. This is especially important with livebearers, goldfish, African cichlids, brackish and many other freshwater fish (which should have an even higher KH over 100-150 or more). In saltwater aquariums your KH (which is generally referred to as alkalinity) should be an absolute minimum of 240 ppm.
The production of Nitrates (via nitric & carbonic acids) will slowly reduce your ph, but a proper KH will keep a more stable ph. This is important to note, if your KH is low and your ph has been dropping, a large water change can cause stress on your fish, or even kill them (don't get me wrong, water changes are VERY important). What is missed by many aquarists is that the pH scale is logarithmic, which means a 1 point drop in pH is a tenfold sing in acid or alkalinity (for more about this please read the pH section).

A proper electrolyte and calcium level, GH, & KH (by the term “proper” I mean what is the best level for the fish kept) can also have a positive effect on the aquarium Redox Balance, which recent studies have shown to be more important to fish and other animal health than pH. Proper positive mineral ion balance contributes to the Redox reduction potential of water, maintaining a more stable water environment, better clarity and the excess electrons attach themselves to free radicals, improving disease resistance. For more information here, please see this article: THE REDOX POTENTIAL IN AQUARIUMS (& PONDS) AND HOW IT RELATES TO PROPER AQUATIC HEALTH

To the left is a map pf average water hardness (combined general and carbonate hardness) in the USA. Please click on the picture to enlarge).


Another consideration of KH is that you can generally safely add the buffers (both freshwater and saltwater) that effect KH without sudden changes in chemistry (unless your freshwater KH is under 50 ppm already), unlike a direct ph or GH change. Maintaining these KH buffers keeps your tanks pH from drastic swings which can be deadly as once alkaline buffers are depleted sudden and dangerous pH crashes are likely (see more about pH later in this article).
The chemistry behind KH is quite complex, so I will not go into detail, however in the most simple terms I can think of; is adding these carbonate (or bi-carbonate) buffers will raise pH to a point of stability and the continued use of certain carbonate buffer “mixes” may raise pH even more (which is why a KH of 50 ppm is all you would want with your discus, while a KH of 200 plus is recommended for African Cichlids or Marine Fish). The rise in pH is related to the ratio of H+ to OH- ions. The CO3- will react with the H+ and eliminate it. This reaction will cause more H20 to break up into H+ and OH- ions. Because some OH- ions were already present, this shifts the ratio thereby raising pH and making the water base (alkaline).
Putting it another way; KH (carbonate hardness) is caused by metals combined with a form of alkalinity. KH (or Alkalinity, which is the more technically correct term) is the capacity of water to neutralize acids and is caused by compounds such as carbonate, bicarbonate, hydroxide, and sometimes borate, silicate, and phosphate. In contrast, noncarbonate hardness (GH) forms when metals combine with anything other than alkalinity.
Carbonate hardness is sometimes called temporary hardness because it can be removed by boiling water. GH (noncarbonate hardness) by comparison cannot be broken down by boiling the water, so it is also known as permanent hardness.

Baking Soda (Sodium Bi-Carbonate HCO3-), is often used for KH, Sodium Bi-Carbonate will buffer at 8.0 to 8.2. Just a little Sodium Carbonate will absorb free H+ ions, and this causes alkalinity (which is the lack of H+ ions).
To stop the Sodium Carbonate ions from consuming too much H+ and to keep a pH of 7.0 we need to restrict the amount of Baking Soda used, as it is always looking for H+ ions to consume. This is why I prefer using products that not only contain sodium carbonates (or sodium bi carbonates), but the proper ratios of other minor elements such as Calcium and Magnesium. Sea Chem Buffers; Marine, Malawi, Victoria and to a lesser degree; aragonite, Seachem Cichlid Salts and Mineral Blocks are examples of preferred methods for KH maintenance.

SeaChem Marine Buffer can be safely used for raising kH (& pH) in freshwater as well (or the Malawi/Victoria Buffer) or you can use SeaChem Alkaline Buffer as both are preferable and safer than baking soda, especially in community aquariums where baking soda can effect mineral equilibrium in a negative way and not maintain as stable of a KH.
The added calcium and other elements keep a more stable & balanced KH/GH and add necessary trace and minor elements. This article will explain a little more about the need for other elements besides Baking Soda (HCO3): "Proper Osmotic Function; Electrolytes".
Wonder Shells are an excellent compliment for raising Calcium, magnesium, and electrolyte levels quickly when used with aragonite or even Baking Soda, however by themselves they do not raise KH much (they are great for Calcium and electrolytes though and for maintaining KH).

Sea Chem Buffers or similar products are better for pH/kH control in livebearer and African cichlids aquariums or a combination of Marine or Malawi/Victoria Buffer and Wonder Shells (Sea Chem Cichlid Salt also compliments Wonder Shells or similar mineral blocks as well).
Before I over promote Wonder Shells, these can aid in proper water management, but they are not a magic bullet in ANY aquarium for poor aquarium husbandry such as mulm build up under gravel or decorations.

Further explanation of common Buffers used to raise KH (& pH)
*Baking Soda (NaHCO3): Is essentially just Sodium bicarbonate and will raise KH, but it can easily be overdosed and does not maintain as a stable a KH or pH
*Sea Chem Marine Buffer: This is multi-ingredient product that not only raises KH and pH, but also GH as it is very balanced in its mineral balance. Due to the ingredients contained there in it will NOT raise pH past 8.3-8.4 even when over dosed unlike Baking Soda. When use in FW, small amounts should be used so as to slowly raised pH and KH as if overdosed you can raise pH to 8.3.
*SeaChem Malawi/Victoria Buffer: This is the same product as Marine Buffer and will also not raise pH past 8.4, even when overdosed (as with Marine Buffer, I have used this product for many freshwater applications such as Livebearers).
*SeaChem Tanganyika Buffer: again a similar product to Marine and Malawi Buffer with additional necessary mineral, however it will raise pH to 9.0 when used full strength.
*SeaChem Alkaline Buffer Buffer: This is more straight forward KH buffer that has less added minerals when these are not desired (often by planted aquarium aquarists). Alkaline Buffer will continue to increase pH as baking soda would if large amounts are used, however it still is more stable and moves pH much less dramatically than baking soda making it still a much better choice in FW.

Crushed Coral/Aragonite
Aragonite or crushed coral is sometimes employed for KH and GH stabilization, however aragonite and crushed coral (as with Wonder Shells) only stabilize KH (they are poor buffers, especially crushed coral) and should not be used in place of a true KH buffer such as Sea Chem Alkaline Buffer when true buffering is necessary due to fluctuating KH or pH whatever the cause may be.

Crushed Coral is primarily made up of Calcium Carbonates (CaCO3) and has VERY LITTLE bicarbonates while Aragonite is of similar make up, but has a much better surface area for dissolving of minerals making it a better choice of the two.
Aragonite is useful at stabilizing a higher kH of around 240 ppm or more, which is the minimum KH (alkalinity) needed for Marine Aquariums, but does not respond to changes rapidly enough when carbonic acids are produced at a rapid rate in an aquarium (usually a high bio load or large amounts of organic mulm will cause this). Even in marine aquariums with aragonite, this may not always be enough to maintain a proper KH (alkalinity) level, especially in tanks high bio loads and without adequate water changes (even skimming can remove some elements). What Crushed Coral are better for is necessary minerals and in the case of Aragonite, it generally has a few more minerals in higher concentrations such as the important mineral (for corals), Strontium.
HOWEVER it often takes copious amounts of acids to free these minerals and what little bicarbonates/carbonates that are available (which is where a Calcium Reactor is helpful in marine aquariums), which is why use of these “gravels” (technically these are coral skeletons) should be used in a “Filter Bag” to “release” these minerals when used in Freshwater, especially African Cichlid aquaria. The use of a filter bag in a high flow area will improve the dissolution rate releasing more minerals and allowing for some buffering, although again I will point out not a lot due to the mineral make up of crushed coral (Aragonite will do a slightly better buffering job when employed in a filter bag).

This said, despite the popular use of crushed coral for pH/KH control in African Cichlids, it is a poor choice for this, especially in high bio load aquariums do to the FACT of its mineral make up (you CANNOT make a mineral appear out of nowhere that does not exist and that seems to be what many mistakenly believe when using crushed coral to increase KH/pH), this is an unfortunate “urban aquatic myth”.
The bottom line is that Crushed Coral or Wonder Shells MAY help maintain KH/pH in a low bio load aquarium, they are best used for minerals (GH) and even here the Wonder Shell is far superior do to the fact it dissolves at a much faster rate and reacts much quicker to chemistry changes in the water than does crushed coral.
Besides the simple mineral makeup of crushed coral, my own tests (especially in marine aquaria) show that its use to increase KH simply is poor!


In lower pH community tanks (6.8 to 7.4) KH buffers such as Sea Chem Alkaline Buffer are still important, however I like to counter these with natural lower pH “buffers” such as Almond Leaves , Peat, and/or Mango/Drift Wood. Buffering your freshwater aquarium is especially important if you have plants fed by CO2 which will raise pH during peak growth times, and there is scientific evidence that GH plays a role here as well; please see this article for more about this subject: “AQUARIUM PLANTS; see PROPER NUTRIENTS ”

Back to baking soda, this is an old stand by method based on the fact that baking soda does raise pH and kH, the problem is there is much new research to show that calcium, magnesium, electrolytes and Redox play a more important role in aquatic chemistry than just pH or basic kH alone (which is another reason good old fashioned water changes often help improve fish health). Unfortunately the aquatics hobby is full of aquarist (especially in forums or uninformed LFS) that regurgitate this old information without checking the facts. If Baking Soda is used, I recommend using Wonder Shells to added needed calcium and other important electrolytes.

If you have a very unstable KH level (drops rapidly), look into causes such as a large amount of decomposing organic material. The more organic break down (de-nitrification), the more acids produced. Some filters if not cleaned regularly can cause this; including canister, UGF, and Wet/Dry.
Please see the section about too low pH and KH problems lower in this article for more about solutions/causes to an unstable KH (near the bottom of the pH section).

For a really informative (and scientific) article about the relation of KH (Buffers) and pH, please follow this link:
pH of buffer - Henderson-Hasselbalch equation
Another interesting scientific thread dealing with KH:

(The following section deals with Calcium specifically

General hardness (GH or dGH) refers to the dissolved concentration primarily of calcium, magnesium and other mineral ions. Both Calcium and magnesium are important for proper internal osmotic processes in fish (and invertebrates). Other ions can contribute to water hardness but are usually insignificant and difficult to measure. When fish are said to prefer “soft” or “hard” water, it is GH, not the KH that is being referred to. GH will not directly affect pH although "hard" water is generally alkaline due to some interaction of GH and KH (it should also be noted that GH DOES effect pH when photosynthesis is thrown into the equation, please see this article: Planted Freshwater Aquariums).
Although many aquarists worry about “too high GH” (based on respiration problems), this is based on long proven false myths. In reality freshwater generally it would take a GH of over 500 ppm to cause this problem. More importantly as to respiration the surface epithelia of gills and body surfaces are protected from direct interaction with the environment by mucous and intercellular junctions. Fish mucous has been postulated to have calcium binding properties. Mucous is a glycoprotein and could serve as a calcium chelating agent retarding ion loss from epithelial cells as a charged surface coat or barrier and thus is dependent on calcium for normal function. Intercellular junctions are specialized areas of attachment between epithelial cells preventing the loss of ions and fluids from the membrane which bathes and surrounds the cells beneath.

GH is an area of aquarium chemistry where there is a lot of misunderstanding or simply down right wrong advice. I have received many a call, email, etc. over the years what do about their so-called high GH, often this GH turns out to be around 200 ppm which is fine for most fish (low for African Cichlids, and even livebearers and goldfish do better at higher GH). This is based on old assumptions of respiration in fish, as well as lack of understanding of the importance of positive Calcium ions (as well as Magnesium & Potassium) in the regulation of MANY bio processes in fish including healing, heart function, and regulation of osmotic functions. GH even plays a role in pH control in planted aquariums (similar processes in marine aquariums, which is why the popularity of Kalkwasser, although GH is not referred to in Marine Aquariums, usually separate Calcium and other tests are performed). I recommend reading the section, “Calcium Carbonate” which explains more about Calcium as well as many of the outside links/references.

This misunderstanding of GH also flys in the face of the best research to date about the importance of Redox in aquarium health and since Calcium and Magnesium play a role in a balanced Redox, understanding that you may have a high GH, YET your aquariums Calcium or other Redox reducers may have given up all possible positive charges (cations) to cells (or other bio processes) under oxidation. It is for this reason, then, that calcium and magnesium supplies MUST be constantly renewed; without this “fresh” calcium, etc. your Redox balance and of coarse fish will suffer.

It is also noteworthy that a GH test is not always an accurate measure of positive calcium and other mineral ions (cations), as with many Ammonia test kits, they are inaccurate after using products such as Prime and give false positive for ammonia NH3 as they cannot discern the difference between the NH3 and NH4+. The same can be said for GH tests that may show a high GH when in reality all positive calcium ions are depleted due to Redox balancing, which is why one MUST constantly supply these mineral cations by whatever means, whether by regular water changes (which often are not enough, ESPECIALLY in small aquariums) or by use of mineral replenishers such as Wonder Shells (which will throw off accurate readings of GH test kits due to their constant supply of positive mineral ions such as calcium!!!).

Think of it this way; a storage battery "works" only when a positive and a negative electrode are present to maintain an electrical current. When the positive plates become exhausted, the battery is no longer any good.

See this article: Redox Balance in Aquariums

Products such as Wonder Shells or similar mineral blocks are excellent for mineral cation (GH) maintenance also the use of aragonite in filters can also be employed for mineral cation maintenance although my experience has shown the method of using aragonite to be less responsive to rapid changes in positive mineral ion needs in FW (especially planted aquariums) than the use of Mineral Blocks.
It should also be noted that your GH may be artificially high from the use of mineral blocks such as Wonder Shells, however much of this is Calcium of which most all fish (fresh and saltwater as well as invertebrates) can tolerate in high levels.

Magnesium is important for proper osmotic functions in fish and invertebrates.
Magnesium is essential for Calcium assimilation, so when magnesium levels are low, the calcium supply becomes exhausted. For this reason, Magnesium is better added in the proper balance with calcium (which both are essential to each other for proper utilization), in such products as Wonder Shells or aragonite sand in a small bag in the filter (although the later is not as reliable).
Magnesium should be part of your overall mineral balance in your aquarium and kept at a level of 1200 to 1400 ppm in marine aquariums (lower for freshwater).

Epsom salts contain magnesium sulfate, are best used for therapeutic reasons such as to aid in flushing the system as it aids in and speeds osmotic function , help to move fluids out of the body. Sulfates, one of the major components of Epsom Salt, have been shown effective in improving nutrient absorption and toxin elimination. Magnesium, the other major component of Epsom Salt, plays a role in the activity of more than 325 enzymes.
That said you would only want to add about 1/4- 1/2 teaspoon per 5 gallons (18 liters). Although useful for therapeutic reasons, magnesium and sulfates in particular are best introduced as part of a greater trace element balance in an aquarium. I ONLY recommend Epsom Salts for therapeutic aquarium treatment. Also note that Epsom salts (as well as sodium chloride; regular table salt) do NOT evaporate or decompose like antibiotics, so only add more after water changes.

Other needs for Magnesium:
• Normal calcium balance in organs
• Healthy muscles
• Healthy nerve transduction
• Healthy calcium balance in blood vessels



Calcium carbonate in your aquarium will keep a more stable electrolyte balance (for osmotic function), while magnesium is another important element that works with calcium. A proper amount of Calcium and Magnesium in your aquarium will affect the fish health positively, including fish such as Discus, German Rams and Apistos!!!. Magnesium and calcium have been shown to increase resistance to degenerate diseases by lowering the acidity in the body. This will help with prevention of ich, fungus, and general “wear and tear” in your fish. Calcium also helps in healing and stress, and without proper calcium levels healing may be difficult or impossible. Calcium is also important and has been shown to both prevent and treat Hole in the Head disease common to cichlids (also referred to as HITH).
The addition of antibiotics (such as Tetracycline) will lower calcium absorption, while the presence of correct amounts of calcium in the aquarium water will considerable reduce the toxic side effects of Malachite Green which is why a GH (for freshwater calcium measurement) of at least 100 ppm or higher is SO VERY important to ich treatment.

In fact I will go a step further as need for Calcium (even in freshwater) seems to be totally misunderstood (I have observed this quite a lot in both scientific and non-scientific observations over the years!). Here is an important quote: “The presence of free (ionic) calcium at relatively high concentrations in culture water helps reduce the loss of other salts (e.g. sodium and potassium) from fish body fluids (i.e. blood). Sodium and potassium are the most important salts in fish blood and are critical for normal heart, nerve and muscle function. In low calcium water, fish can lose (leak) substantial quantities of these salts into the water.” See reference below.
Understanding Water Hardness.
In freshwater aquariums I recommend a minimum of 100 ppm of calcium (which a GH of 100+ ppm will generally provide).
Please also read this article from Aquarium Answers as well, as much of what is contained in this article relates to the importance of Calcium and other minerals as well:
Proper Osmotic function, Do Fish Drink?

Another note about calcium; Calcium is very important to proper discus health, yet calcium can adversely affect the kH of a discus aquarium when combined with sodium carbonates or bi carbonates, which is generally kept at a pH below 6.5. I have successfully used calcium such as Wonder Shells, in discus aquariums by using a mix of RO (Reverse Osmosis) water and tap water (dilution will vary depending on your tap and tank water parameters). I then add electrolytes to the RO water and add peat to the filters. I have used this method successfully with discus and added the needed calcium with no pH climb.

Calcium is also a major Reducer with a negative 2.87 electron reduction rating, and plays an important role in maintaining a healthy aquarium Redox Balance that is a VERY important aspect of true water quality

Finally, back to the aspect of Calcium (& magnesium which should be 1200- 1400 ppm) in general is if these important elements are in “short supply” besides the before mentioned problems, an aquarist may also see pH swings a few hours after the lights go on as the process of Photosynthesis in algae will increase pH during daylight hours if low levels of calcium and magnesium are present (as noted earlier in the GH section as per studies). Keep in mind that a pH swing from 7.8 to 8.2 (as is common in this situation) is four fold increase in pH since the pH scale is logarithmic.

Other needs for calcium:
• Calcium is a vital component in blood clotting systems and also helps in wound healing.
• Calcium helps to control nerve transmission, and release of neurotransmitters.
• Calcium is an essential component in the production of enzymes and hormones that regulate digestion, energy, and fat metabolism.
• Calcium helps to transport ions (electrically charged particles) across the membrane.
• Calcium is essential for muscle contraction.
• Calcium assists in maintaining all cells and connective tissues in the body.

For further reading about Calcium and other minerals, please reference these articles:
This one is great
Understanding Water Hardness

A very well informed forum post:
Calcium and Osmoregulation

For relationship of mineral bio-availability when positive and negative ions are considered:

For more information about how Calcium, pH, GH, and KH relates to ponds, please see this article about Ponds: A Clear Pond; Pond Information

Calcium/ Kalkwasser/Magnesium in Marine Aquariums

Your Calcium level should be a minimum of 400 ppm for marine. For saltwater aquariums, I recommend Reef Calcium; polygluconate along with the use of aragonite sand or crushed coral for calcium level maintenance (Calcium Generators also work well for advanced aquarists).
Although Kalkwasser is popular among many advanced marine aquarists, caution should be used with this method of adding calcium to your marine aquarium (this is not to say Kalkwasser does not work, in fact introduced properly it is an excellent way to regulate calcium and alkalinity in saltwater aquariums).

Here is how Kalkwasser works:
Used properly Kalkwasser (Calcium Hydroxide) is slowly dripped into your aquarium, it captures free Carbon Dioxide present in the tank water and converts it to Bicarbonate ions. However if you drip too fast or if there is not enough Carbon Dioxide available in the water, Carbonate ions will be formed which will make the Ca++ you are trying to add to your tank get wasted by the useless precipitation of Calcium Carbonate (often forming a white residue that precipitates out of your aquarium). Too rapid addition of Kalkwasser may actually cause the Calcium and Alkalinity in your tank to go down instead of up. See the equation below:
Ca++ + 2(HCO3-) + Ca++ + 2(OH-) <==> 2 CaCO3 + 2 H2O

Often even a slow drip of Kalkwasser (Calcium Hydroxide) can cause the above reaction if there is not enough CO2 present in your marine aquarium. One method to avoid this is to add 15ml of 5% Distilled White Vinegar (Acetic Acid) into a 1 liter or 1 quart container. Dissolve 1/2 teaspoon of Kalkwasser into the Acetic Acid, and then dilute to 1 liter (1 quart) volume with either RO/DI water (tank water can be used in a pinch).

Calcium Reactors for Reef Tanks:
As noted earlier in the Kalkwasser section, a Calcium Generator/Reactor is an excellent idea for maintenance of calcium and alkalinity as well as KH/pH regulation, especially in marine/reef tanks heavily stocked with stony corals. A calcium Reactor works by providing a steady stream of calcium by using CO2 in the reactor.
The advantage is similar to the simple Wonder Shells in freshwater (except better in my opinion); it provides an essential positive calcium ions, that are often exhausted , even when tests show calcium still present in the aquarium (See the section in red font in the GH section of this article).

About Plaster of Paris for calcium (also Lime):

Plaster of Paris is often recommended as a source of calcium for ponds or aquariums in place of aragonite, Wonder Shells or similar, this is NOT a substitute for Wonder Shells aragonite or similar and is not the same!
Plaster of Paris is a poor choice for GH or Calcium as Calcium needs to be in the proper ratios with other elements such as Magnesium to be utilized by aquatic life (such as osmotic function).
Lime is also similarly recommended for ponds for KH and pH, however it is simply CaO and does not contains other elements necessary including bi-carbonates and magnesium to name but a few.

Here is a list of ingredients of Plaster of Paris:

*CaSO4 , 1/2H2O: 97.97%
* SiO: 0.94%
* Al2O3: 0.69%
* Fe2O3: 0.28%
* MgO : 00.12%

For a further explanation of Plaster of Paris in aquariums and Ponds, please read this article: THE DIFFERENCE BETWEEN PLASTER OF PARIS AND PRODUCTS SUCH AS WONDER SHELLS OR SEALAB


Electrolytes are molecular substances containing free ions which behave as an electrically conductive medium. In fish (or other living things) the primary ions of electrolytes are sodium (Na+), potassium (K+), calcium (Ca++), magnesium (Mg++), chloride (Cl-), phosphate (PO4---), and hydrogen carbonate (HCO3-).
Fish and other aquatic life forms such as shrimp require a subtle and complex electrolyte balance between the intracellular (inside the cell) and extra cellular (outside the cell such as plasma membranes) environment. In particular, the maintenance of precise osmotic gradients of electrolytes is important. These gradients affect and regulate the hydration of the fish, blood pH, and disease resistance and are important for proper nerve and muscle function.
Salt is commonly used in a dose of one tablespoon per 5 gallons (20 liters) in freshwater aquariums. This is one way to add some electrolytes, but this should not be the only (Wonder Shells add many other electrolytes which is a reason I strongly recommend these, especially in smaller tanks such as with Bettas). Salt also will aid in disease prevention as it will help with the generation of the slime coat (or Mucous) on fish as salt acts on the osmotic gradient. But care needs to be given with salt sensitive fish such as catfish not to exceed this amount. Another aspect of salt is that although it aids in the prevention and even treatment of Freshwater Ich (Ichthyophthirius multifilis), it is poor treatment for a full blown infection despite many anecdotal comments by many.

The importance of electrolytes/trace elements in Marine aquariums is magnified since most marine (saltwater) drink the water around them. Depletion of these trace elements through biological processes needs to be compensated for by water changes using a quality marine mix AND by testing your alkalinity (KH)/Calcium/Magnesium and adding buffers such as Sea Chem Buffer accordingly that not only add necessary carbonates for buffering but also add necessary electrolytes such as Chloride, Calcium, and Magnesium to name a few.

For MUCH more on the effects of electrolytes and their function in freshwater and saltwater:
How do Fish Drink; Proper Osmotic Function

Further Reading/references about the importance of Electrolytes in all organisms (including fish and humans) fluids and electrolytes.htm


Although this articles main subject is not about pH, it is hard not to mention a little something here. Often aquarists will “chase” pH trying to achieve the “perfect” pH not realizing that pH stability is generally for more important than the actual pH number. Fish can adapt to different pH, however fish are NOT tolerant to wide swings in pH.
There is a simple explanation to this that many are not aware of, that is the pH scale is logarithmic, meaning a change of pH from say 7.0 to 6.0 is a ten fold increase in acidity, while a change from 7.0 to 5.0 is 100 times change in acidity (it also goes the other direction as to alkalinity). This is also why large water changes (25% +) are generally a good idea unless pH (and GH) levels are not changed (this also why cleaning filters such as the Aquarium cleaning Machine are useful for tanks with high bio loads that may require larger water changes). This is also an important reason to not only float your new fish for temperature adjustment, but to also slowly introduce aquarium water to your new fish’ shipping bag prior to tank introduction.

Reference: Elmhurst Education; pH

KH as noted earlier is a stabilizer of pH (towards the alkaline side) whereas peat, some driftwood, Mango/Drift Wood , and dried almond leaves (Bio Lif ) will aid in lower stabilization (for really troublesome high pH aquariums, cutting pH/KH with blended RO water may be necessary, see below).
Please note that Peat, Driftwood, etc. mostly lower pH via release of acids such as Tannins, and that if your carbonates are high (KH) your pH will remain high (please read more about this in the Amazon River Water section)

If using Bio Lif or Peat (I recommend Bio Lif), I suggest at least temporarily suspending the use of carbon, you can still use it, just not after initial use of Bio Lif or peat as Carbon removes many of the elements that these products add that make them work (much like how carbon can remove other essential trace elements and non-essential trace elements and toxins (carbon cannot tell the difference between good and bad). If the water gets too brown from these products, then slowly re-introduce the carbon back in.

For Amazon/SE Asia River Water (lowering pH)
For Fish such as Discus, Bettas, German Rams, Apistos (Apistogrammas);

For areas with high KH or pH problems the use of RO or DI water blended with tap or well water is simple and effective method to solve this problem (combined with pH/KH buffers discussed later). Do NOT use products such as pH down. Simply adding sodium bisulphate (HCl) will lower the pH, but will not keep a stable pH which is much more important than the actual pH.

RO (Reverse Osmosis) or DI (De-ionized) water is used to aid in pH (& KH) reduction.
I would recommend only using no more than 25% to start with the remaining 75% well or tap water (although for advanced aquarists that are confident in their use of mineral and electrolyte replacements may use much more RO/DI); then and adding a Wonder Shell for about a day to this water to add back essential minerals (and/or other forms of trace elements such as API Electro-Right, SeaChem Replenish or Tropic Marine Pro Discus Mineral, with the later two being the better products IMO over Electro-Right).
Calcium is also very important to Amazon basin fish as well as other fish too (despite some old school commentary to the contrary) and does not directly effect pH only GH. Please refer to the section about Calcium earlier in this article as to why.
Calcium should also be included and many electrolyte replenishers (such as Electrolyte) do not add adequate amounts of Calcium (only trace electrolytes such as found in the before mentioned Electro-Right). Please note that I am not putting down these products, as I have used them and they are very good for replenishing this important electrolytes including some chlorides Wonder Shells may miss), they are just not complete as per continual replenishment of positive calcium canions (necessary for Redox health). Wonder Shells can also be used with these products to provide better balance in this area.

You can adjust this percentage up with subsequent water changes as you find your “sweet spot” in pH, but remember that pH stability is often much more important than the actual number. Also be careful in using bottled drinking water assuming it has proper minerals, it usually does not.

Be patient with this process as you want slowly lower pH (and KH well), as earlier stated you can increase your percentage of RO or DI water each time you change water however you do not want stress fish by a large RO percentage right away.
Also keep in mind that Peat, Bio Lif , and Mango Wood/Driftwood will slowly work on pH and KH reduction, NOT overnight! These products act as low pH buffers and will not bring down a pH immediately (nor do you want to either!), if your KH is especially high this will take time and subsequent water changes with blended RO water (which will “cut” the pH). However you can boil peat in a pot or Bio Lif (almond Leaves) to release all the acid faster.

As I noted earlier in the general pH section, is although Peat, Driftwood, Bio-Lif or similar Almond Leaf products will lower pH, it is done via the production of acids such as tannins and if your tap or well water used is very high in carbonates or bicarbonates (which are KH buffers) you will see NO effect on your pH and you will need to remove these KH buffers for these to effective or allow for time as the tannins slowly dissipate the carbonates via interaction with the acids/tannins. This is why I generally used blended RO/DI water as noted earlier for my water changes for my clients in the LA area where high carbonate tap-water was a way of life.

Other products for softening water such as Atison’s Spa, Bio Lif, etc.
Other products that are popular for softening water, lowering pH, and for creating an Amazon or Breeding environment include black water tonics and Atison’s SPA. I personally do not care for the old black water remedies as I find them to mostly work like the proverbial “chicken soup” placebo effect when put to actual tests and in fact I have seen harmful anaerobic bacteria added from these remedies.
As to Atison’s SPA, this is growing in popularity among Betta enthusiasts due to mega internet site promotions by Dr. Fosters and PetsMart. This is a good product as per the use of Almond leaves that it contains which are vastly superior to Black Water or peat, however it is very refined as compared to the superior Bio Lif and its claims to help with Calcium (which is often a forgotten mineral necessary for healthy breeding) is vastly better served by a separate addition such as with Wonder Shells with will add a constant supply of important mineral cations that are essential for fish or even water changes using high calcium water or salts that contain calcium such as SeaChem Cichlid Salt.
Another aspect of this product is that the almond leaves are very refined which causes the loss of potency of beneficial attributes and that it contains added Sodium Thiosulfate which although is an excellent de-chlorinator is unnecessary in a product such as this in my opinion. Personally I would avoid the hype of the Dr. Fosters at al and stay with products that more professionals use such as Bio Lif and Wonder Shells (most of the breeders I know especially in LA use Bio Lif or similar do to better results over “Spa”, however these guys are not active in Betta or Discus groups/forums, so this does not get out.

Finally it is important as you also want to note that the Amazon River starts high in the Andes Mountains where it picks up a lot of minerals only to be buffer “down” by organics such as peat and bio-decay (as well as dilution from copious amounts of rain water).
Bio decay will also add nitric acid which will further lower pH (providing you do not over clean the substrate). Because of this, do not try and lower GH (only carbonate hardness), calcium in particular as this is still an important element for osmoregulation in Discus and other Amazonian fish as well (calcium aids in a reducing Redox as well!)

Do NOT use pH lowering products such as pH Down as these will just cause a roller coaster effect on your pH, better to concentrate on a stable KH and use blended RO water along with pH buffering products such as Bio Lif (almond leaves), peat and Drift Wood (Mango Wood).

Back to pH in general:

The main point I would like to make as to pH is that often too much concern is given to a perfect pH when in reality a stable pH is more important (which I can speak to in the 1000s of aquariums I have maintained at different pH and other parameters). I have seen Discus (a fish which comes from waters often under 6.5) breed in aquariums with a pH above 7.5. What is stressful is a pH that is not stable therefore a good KH or acid buffer is important. What I have found FAR MORE IMPORTANT is electrolytes and calcium (which will also affect a good Redox Potential) present than a so called perfect pH. The discus under my care were much more healthy with a KH of around 50 ppm, a GH around 100 ppm and a Redox Potential around -300 mV than with a pH under 6.5 (please note that these numbers just given are for discus, for many fish such as livebearers I kept a much higher KH and GH).

Another point to pH is tap water or well water pH when drawn will often gas out (sometimes referred to as “gassing out”). This is trapped CO2 gas in the tap water (also Hydrogen Sulfite as well) that will slowly gas out of the water if allowed to sit.
What I mean is you will get a sample of tap/well water then immediately test it and get a result such as 6.5 that can rise to 7.0 or higher over the next hour as CO2 gasses out, if there are carbonates (KH) in the water (even more common in well water from my experience), the pH will rise (sometimes appreciably).
This is noteworthy in testing your tap water as you will NOT get accurate tap water pH readings if you test your water immediately after drawing it from the tap, it is best to wait at least one hour. This gassing out does NOT affect GH or KH as these are minerals that remain in the water.

The addition of mineral blocks such as Wonder Shells would not cause a problem as these would not add more carbonates to water already containing carbonates at level of 150 ppm KH for example. Again, stability is the key point and adding phosphate containing pH lowering products will tend to cause roller coaster pH swings in an established tank. Better is a stable GH and KH with the addition of (Bio Lif ), Peat, Driftwood, and/or Mango Wood .

Corrections for unstable KH/pH
(or too low pH or KH problems):

First start by testing your tap or well water (as stated earlier this can gas out so wait for 1 hour before testing). If your tap/well water is low in pH and/or KH you will have problems maintaining higher pH if that is desired. Areas that draw their water from rivers, especially that flow in boggy areas or are of volcanic origin may have very low pH/KH. If tap/well water is the problem or part of the problem you will need to add some crushed coral/aragonite to a nylon bag and place this in the filter AND/OR you can add can add some Buffer to the water (I do not recommend Baking Soda as noted and explained earlier in the article). A complete buffer such as Sea Chem Buffer (Marine OR Freshwater) will work well as this supplies ALL elements necessary and much more steadily than crushed coral/aragonite (the Marine is safe for FW use and I actually prefer it over the Rift Lakes Buffer). Wonder shells will help with Calcium and GH and will help maintain KH, however they are NOT as useful for water that is already very low in KH/pH and needs to be brought up. For planted aquariums I prefer the Sea Chem Alkaline Buffer, although this product is not as stable as marine or rift lakes buffer as this buffer is more basic like Baking Soda so regular checks of KH are more important when this buffer is employed.

If the tap/well water is fine, I would look at tank conditions and change more water, more frequently. Here are a few possible problems to look into:

*Too high of DOC (dissolved organic compounds) caused by organic debris/mulm, this can be spotted by a KH of (for example) 50 ppm after cleaning, addition of buffer, and correct out of the tap, however if KH drops rapidly after the initial measurements. Increasing the frequency of filter media rinsings (in cool de-chlorinated water though, so as to preserve nitrifying bacteria). This may mean rinsing as often as twice a week and this includes filter media inside bio bags (Whisper), carbon inserts (Aqua Clear, Internal Wet/Dry), etc.
*Mulm buildup under rocks/décor and in canister filters/ Wet-Dry filters. Canister filters in particular if let go more than 6 weeks can buildup a lot of decomposing mulm that will add acids to your water.
*Too much Driftwood/Mango Wood. Some driftwood in particular can be full of tannins that will lower pH/KH.
*Too deep a sand bed, this again can add to decomposition that leads to acid build up (sand tends to worse than gravel here, however gravel can cause this too when too deep.
*In frequent or poorly conducted water changes/cleanings. Please see this article for more: “Aquarium Cleaning; Methods and Reasons”
*Even an otherwise normally good #3 grade of gravel that is regularly vacuumed may still harbor organic mulm, this is particularly rue of many epoxy coated colored gravels as this coating often starts to loosen and allow organic mulm to be trapped there resulting in rapid KH depletion!
The solution is to often remove ½ the gravel at a time (so as to cause as little interruption of the nitrogen cycle) and either change (usually in the case of colored gravel) or thoroughly wash it.

After correcting these problems, you still may need to add a buffer or aragonite bag to your aquarium.

The Green Lane (

Here (below) is an interesting chart and calculator for the relationship between KH and pH as it relates to CO2 in planted aquariums:
Measuring CO2 levels in a Planted Tank


• All fish require calcium and other mineral cations, including discus, bettas, tetras and other soft water fish. In fact the lack of electrolytes and calcium is a MAJOR problem for poor health in bettas and discus. Good water management should ALWAYS insure good electrolyte levels along with water changes and other aquatic husbandry practices. Use of water conditioners as well mineral blocks can help insure this.

• Calcium and other minerals added to fish food made from poor quality ingredients are usually not adequate for proper health (some studies show these added minerals block absorption). Calcium and other minerals in the water (especially for marine organisms) as well as foods high in natural minerals such as Spirulina are also important.

• Although the addition of calcium and electrolytes may initially stress fish that have had low electrolyte levels, this does NOT prove these elements detrimental any more than changing water in an aquarium that is long over due for a water change (this too may initially stress fish). A GH of 20 dGH (over 350 ppm) is easily tolerated by ALL fish especially when calcium makes up the majority of this separate calcium and magnesium tests can verify this)

• Although RO or DI may be very clean and pure, by itself it can be VERY detrimental to fish without the addition of electrolytes and trace elements such as calcium. If you use it, make sure you reconstitute it. I only recommend using RO/DI blends with tap water (and then generally in low pH fish such as discus, adding a Wonder Shells or similar for added trace elements). Drinking Water is usually just RO water with SOME minerals added for “taste” and is FAR from appropriate for aquarium use. Usually true spring water is OK. However RO or DI water is fine for marine use (in fact I recommend it) as salt mixes add all the trace elements needed

• It is possible to have adequate calcium and electrolytes without raising pH to a harmful level for discus, bettas and other fish that generally prefer low pH water (many discus breeders in LA keep there discus pH higher than in the wild anyway).

• You can help lower your pH without affecting Calcium and other electrolytes with many types of driftwood, such as Mango Wood/Driftwood , peat or peat pellets, and /or my preferred method Almond leaves (or husk) placed in a filter or filter bag as these not only lower pH, they also help with water quality especially the control of dangerous anaerobic bacteria. A product which contains them in a refined and usable form is Bio Lif . This said about the use of these products, I personally find that the almond leaves, peat, and driftwood work best as an aid to low pH maintenance and lowering the pH first by partial use of RO or DI water works best.


I should note immediately that these suggestions are NOT meant to be the only way, these are simply suggestions based on experience and good science/research.
What is most important is not the how, but the FACT that many mineral cations are essential for fish health from Freshwater Discus to Marine Reefs. Often experienced aquarists do not take extra steps to provide these, yet they inadvertently provide essential positive mineral ions and carbonates via good aquatic husbandry, substrate choices and more.
However it is not correct to state that just because one does not take extra measures, others should not as well. Also, it is noteworthy that even experienced aquarists may not be maintaining the best environment possible, as statements such as: “I do not maintain or check my positive mineral ions (via a not always reliable GH test) and my fish are fine” prove absolutely nothing, as many fish adapt to poor environments but do not thrive as well as they could and good science states otherwise to such statements.

Basic Widely Mixed Community, including Tetras, Gouramis, Catfish, Loaches, Danios, Livebearers, many Cichlids, etc;

*Aim for a pH that is stable (not an exact number) in the range of 6.6 to 7.8.
*A KH of anywhere from 80 to 150 is generally good and this can be maintained with products such as Sea Chem Buffer OR Sea Chem Salt (I recommend an either or for a mixed tank, if Buffer is used a plain Sodium Chloride salt such as water softener salt is best). If tap water is high pH/KH I would recommend using 10-20% Reverse Osmosis Water and/or products such as Bio Lif or Mango/Drift Wood to counter the high pH/KH.
*GH is best between 150- 300, although this can be misleading in that CaCO3+ (& other positive mineral ions) can be depleted and your GH still reads high. The use of Wonder Shells can help with this (although 1-5% water changes daily can help as well provided your water source has these important mineral cations)

Soft Water Low pH, KH Amazon River or West African Aquarium

Since I already have a whole section earlier in this article, I will refer back to it


*Aim for a pH that is stable, as before, not an exact number but in a range of 7.2 to 8.4 should be fine
*A KH of anywhere from 150 to 250 is generally good and this can be maintained with products such as Sea Chem Buffer and Sea Chem Salt The difference from the mixed community tank is that mixing Cichlid Salt (which also contains buffers) along with basic buffers is fine, although you obviously want to test your KH to find the “sweet spot” in the amount needed to fit your bio load and tap water adjustments.
*GH is best between 250- 350, although again this can be misleading in that CaCO3+ (& other mineral cations) can be depleted and your GH still reads high.
The use of Wonder Shells can create a constant supply of necessary positive mineral ions and the use of crushed coral gravel can supplement this further if desired.

Rift Lake Cichlids

Similar to livebearers, except many aspects should be often higher yet in alkalinity/pH, especially for Lake Tanganyika Cichlids.

*Again, aim for a pH that is stable, as before, not an exact number but in a range of 7.8 to 8.4 should be fine for most Malawi or Victoria Cichlids and 8.0 and higher for Lake Tanganyika Cichlids.
*A similar approach to livebearers except the goal is for a slightly higher KH (more so with Tanganyika Cichlids) with a KH of anywhere from 150 to 300 being generally good and this can be maintained with products such as Sea Chem Buffer AND Sea Chem Salt
*GH is best between 250- 350 (or even higher) and as stated before, do NOT depend on your GH test kit to give you the full picture of the yet even more important for Rift Lake Cichlids mineral cations. These large lakes have a large in flow and reserve of these ESSENTIAL positive mineral ions that CANNOT be easily duplicated in an aquarium, eve with the use of crushed coral gravel (although this is certainly a good start). The use of an even more fine oolite coral sand is eve better for supplying these mineral cations important for osmoregulation, Redox Balance and in the end good fish health.
The use of Wonder Shells can help with a more steady supply of these mineral positive electrolytes.
Regular water changes, especially with high mineral water (often tap water is great for this) should NEVER be over looked as well.


There is much scientific practical evidence to support the need of Calcium, a healthy KH, GH, and Electrolytes in a Freshwater Aquarium. This is more widely known for marine aquariums, however these important parameters and the interaction they have on fish health in freshwater are often missed. The minerals often found in GH (Calcium in particular) have also shown to be effective for BOTH prevention and treatment of Hole in the Head (HITH) in many cichlids

Many freshwater aquarists will often concern themselves with a certain pH all the while missing the importance KH plays in the stability of pH even in Amazon River tanks (where low pH buffers should also be employed).

The need for calcium by all creatures is well documented, especially in studies outside the aquatics industry/hobby. Calcium and other elements found in a healthy GH are important for osmoregulation in ALL freshwater fish and even plants (saltwater organisms too). These elements also aid in a healthy Redox Balance as well. The addition of pH up or pH down products is often counter productive vs. using products that stabilize your aquariums KH and GH, these products often result in a bouncing pH.

Products such as Wonder Shells will help with your calcium (especially important CaCO3+ which are quickly depleted, even when GH tests kits show abundant Calcium/minerals the beneficial positive ions may be depleted), magnesium, GH and aid Kh of your aquarium. I prefer them over crushed coral for adding calcium, magnesium and electrolytes as from my experience.
Wonder Shells also are available in a medicated version for control of aquarium ich and fungus.

161 Posts
Discussion Starter · #7 ·
So, I guess the bottom line is that plants don't really care for KH. But for the sake of fishkeeping and invertebrates, it would be best to keep KH above 2-3 degrees because it improves the Electrolyte, Redox and Osomotic function of fish because fish are by nature are alkanline? Is this a fair statement?

1,062 Posts
I guess question number one is what sort of water are you using with ~0 KH? I use 80-90% RO water and still can't get it below 5deg. I would say that for 99% of the cases, the tap water coming out of a person's faucet is good enough to be used without buffers.

161 Posts
Discussion Starter · #9 ·
Wow! 90% RO/DI water and still 5dKH? Your tap water is like liquid rock... I guess I'm fortunate to have near zero KH from my tap. I use API KH test kit and it would turn blue with the first drop of reagent. Even if I dilute with 50% distill water, it would only take one drop.

1,062 Posts
Wow! 90% RO/DI water and still 5dKH? Your tap water is like liquid rock... I guess I'm fortunate to have near zero KH from my tap. I use API KH test kit and it would turn blue with the first drop of reagent. Even if I dilute with 50% distill water, it would only take one drop.
I would test my tap water with my API test kit, but i'd be afraid of the reagent running out! I've heard from my LFS that it's in the 20-30dKH range on average. The only difference between our tap and cement is the cost! :hihi:

I'm not exactly the most intelligent person on the forum when it comes to water parameters, specifically raising hardness, so i'll not make a fool of myself by trying to solicit advice.

1,742 Posts
I would love to have New York City water. It's alot easier and cheaper, to put magnesium and calcium into the water than take it out.

Redfalconf35, are you using your own RO unit or are you buying RO at Meier (grocery store). If you are using your own RO unit, how long do the cartridges last? I lived in Indianapolis for 3 years. I had to use a chizel to get the water spots off the glasses. LOL

1,062 Posts
I'm actually using my own unit... I got a cheapo one off the internet a couple months back, and besides breaking it on assembly, i've had good luck with it. It leaks a bit, but other than that it works fine! As far as the cartridges lasting, i'm actually not sure. I would guess somewhere around a year give or take. I think they are rated to 10000 gallons (i'd have to check the manual).
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