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post #1 of 46 (permalink) Old 10-10-2014, 01:00 PM Thread Starter
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Kh?

KH?

One day I read that certain crypts have no tolerance for kh. Another day I read that certain plants can take up carbon from the kh available in the tank. When I ask people about adding carbonates as a source of carbon they tell me that wonít work. Can somebody explain to me what is going on here?
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post #2 of 46 (permalink) Old 10-10-2014, 01:31 PM
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I think there's some minor technical confusion.

Some folks try to add carbonates, in hopes that it will increase their CO2 levels. After all, if you can raise your KH without raising pH, you've raised CO2 right? Wrong, this won't happen. You've added carbon in carbonate form, which is not the same as CO2, and the carbonates raise your pH anyway. Any "increased CO2" is a byproduct of non-carbonate buffers stabilizing the pH, but there's been no CO2 created, it is just showing the minor inaccuracies of using pH/KH to determine CO2 levels.

I think most folks are assuming you are asking if carbonates will add CO2, since this is a common mistake.

There are plants out there that can use carbonates, but not all do, and most do this inefficiently. It also can lead to calcium/magnesium deposits building up on the leaves if it goes on too much. (see deficiency finder's images of severe CO2 deficiencies)

Adding carbonate shouldn't be a preferred way of getting your plants carbon. However, it helps to be aware that if your plants are starving for carbon, some of them will start raiding your carbonates, as this can have adverse effects on your pH.

Last edited by mattinmd; 10-10-2014 at 01:33 PM. Reason: added note on raising pH and pH/KH mistakes
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post #3 of 46 (permalink) Old 10-10-2014, 02:13 PM
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The efficacy that plants can extract carbon from carbonates varies from plant to plant. Plants have evolved based on their environments. Aquatic plants from very soft water environments can't effectively extract carbon from carbonates. Others who evolved from hard water can since there are ample carbonates to draw from.

Technically, adding carbonates can provide carbon to plants that have the ability to extract carbon from HC03. I say technically, because this process comes at a great expense. The energy required to extract carbon from carbonates is very high. Plant growth will be far less when plants are forced to used carbonates.

CO2 is the preferred carbon source since it requires the least amount of resources to utilize. It also can be used by all plants unlike carbonates.

Some crypts may not be able to use carbonates where others can. It depends on the plant itself. Adding carbonates (only if they're near zero btw) can supply carbon. However, CO2 is far better source of carbon.
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post #4 of 46 (permalink) Old 10-10-2014, 02:54 PM Thread Starter
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I'm not really interested in adding co2 that is part of the point. The fact that it might be better in some way isn't relevant if I am not adding it at all.

Your saying "adding carbonates (only if they are near zero btw)" what does that mean?
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post #5 of 46 (permalink) Old 10-10-2014, 04:49 PM
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I believe Zorfox trying to imply that increasing the concentration of carbonates does not make it easier for plants to absorb them. They just need to not be absent.

ie: going from 0dKH to 2dHK is probably helpful, as you are going from absent to present. Going from 2dKH to 8dKH probably makes little difference (if I'm getting Zorfox's implication).

That said, you don't need to add pure CO2 (ie: pressurized CO2 tank or DIY yeast) in order to add CO2 to water. Using an airstone/airpump and/or vigorous surface agitation can prevent the water from being completely depleted of CO2 in low-tech setups.

You will only get very low concentrations of CO2 this way, a few ppm. However, maintaining a few ppm of CO2 it is certainly far better than allowing the CO2 to deplete down to zero and getting to the point plants will start using carbonates.

If I gave you an all you can eat buffet where you could only take a tablespoon of food at a time before going back to your seat and eating it, would you eat the buffet or go out and scavenge for ants in the yard to eat as a survival food? There's a lot more calories per hour at that buffet...
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post #6 of 46 (permalink) Old 10-10-2014, 05:00 PM Thread Starter
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I can’t tell you how many people have told me that adding an air stone or extra surface agitation has no impact on co2 in the water.
Let’s try this point of view. Why would kh be harmful? Is it simply the effect on the ph? Or is there something about the carbonates that interferes with the health of the plant. This is a common claim in regards to certain blackwater crypts. What is going on there?
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post #7 of 46 (permalink) Old 10-10-2014, 05:51 PM
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Well, they are right, assuming the tank has no plants in it. (ie: they oversimplified the problem).

Adding an airstone won't raise the CO2 level above what the water would achieve just sitting around in a bucket for a few days. It will reach equilibrium with air, and that's it. Aeration won't raise CO2 levels beyond this point, no matter how hard you try.

However, in planted aquarium you've got plants consuming the CO2 out of the water when the lights are on. The plants *WILL* drive that CO2 level downward, when the lights are on, if there's no aeration going on.

Really, the best aeration can do is preventing the CO2 from going down below equilibrium levels. So, keeping CO2 steady at 3ppm, instead of dropping from 3ppm to 1ppm could be called "no impact", particularly when spoken by someone who uses pressurized CO2 to go up to 30ppm.

As for adverse effects of KH... I don't know. I'm no expert on blackwater crypts. That said, it should not be too surprising that some plants are intolerant of high levels of things that other plants find necessary to survive. Life forms are amazingly diverse.

Is it really the Carbonate? The resulting pH? The high GH that often accompanies high KH (assuming calcium/magnesium carbonates)? The high sodium that accompanies adding sodium bicarbonate to make a high KH/low GH water? Any of these are possible in my mind, but I don't know the actual answer. Perhaps someone else can.
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post #8 of 46 (permalink) Old 10-10-2014, 09:28 PM
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Originally Posted by mattinmd View Post
I believe Zorfox trying to imply that increasing the concentration of carbonates does not make it easier for plants to absorb them. They just need to not be absent.
That's exactly what I meant.

There are a handful of plants that simply won't do well in hard water. Personally, if a plant won't thrive in my tap water I don't grow it. Of course that's my personal choice as in any hobby. Greater than ninety percent of the 300 plus varieties we have access to will grow in nearly any water. I choose to concentrate on that palette rather than changing the world to accommodate a select few. Maybe one day I will but for now...not so much.
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post #9 of 46 (permalink) Old 10-10-2014, 09:50 PM Thread Starter
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So then are we to assume that the plants are not using the carbonates to any meaningful extant? Would say a tank full of Vals not change the kh ?

I assume that anyone who adds chemicals to a tank or co2 for that matter is changing the chemistry of the water so I don't really understand that point. All of the plants I grow grow in my tap water.
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post #10 of 46 (permalink) Old 10-10-2014, 10:05 PM
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So then are we to assume that the plants are not using the carbonates to any meaningful extant? Would say a tank full of Vals not change the kh ?
A tank full of any plant that can extract carbon from carbonates will change the KH over time if there is no other carbon source. However, the efficiency of carbonate carbon versus CO2 is exponential. It's like comparing oranges to apples. Plants will use carbonates when they are forced to. If we do simple water changes the carbonates used will be replaced.


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I assume that anyone who adds chemicals to a tank or co2 for that matter is changing the chemistry of the water so I don't really understand that point. All of the plants I grow grow in my tap water.
They are changing the chemistry. Adding CO2 vastly improves plant growth even with low light. Adding glut also improves plant growth. Don't confuse the tap water chemistry with fleeting CO2 levels. Plants are comprised primarily of carbon. That carbon is best supplied by CO2. The KH or GH is far down on the list as far as plant appetites are concerned. Give them adequate CO2, light and nutrients and they will do well in nearly any basic water chemistry.
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post #11 of 46 (permalink) Old 10-10-2014, 10:23 PM
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Seems to be a problem with the definition of carbon? Carbon and carbon compounds are all over the map. Just because you read that carbonates have carbon and that they don't help does not mean that ALL carbon is good or bad. Rubber tires are one form of carbon that most would agree is not needed in our tanks to make plants grow. One has to dig deeper than just seeing CARBON as good or bad.
I find step one of understanding things I read on the internet is to check if it is reliable info.
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post #12 of 46 (permalink) Old 10-10-2014, 10:26 PM
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Smile Aeration is the Key

Hi,

In as much as I am not the confrontational or argumentative sort, let me offer a clarification.

Our aquariums, in use presumably cycled, are quite different from buckets.

{Mythical standard day, no significant interferences.}

Simple aeration will raise the CO2 levels of an aquarium, especially in mature systems with 6-centimeters of sand, dirt, clay or combination thereof.

In well-aerated tanks 5-6-ppm CO2 are common, can go as high as 9-ppm CO2. May have to test this with the lights out, then remember the CO2 will be higher since plants are net producers when photosynthesis is not taking place.


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post #13 of 46 (permalink) Old 10-10-2014, 10:42 PM Thread Starter
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I am not really interested in efficacy or efficiency. I am interested in KH and what it is doing in the tanks and how it is interacting with the plants. I am not really sure why this conversation need involve co2 or glut at all.

What is it about carbonates that causes problems? Is there a benefit to using say KHCO3 instead of CaCo3? Is the calcium the problem? etc.
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post #14 of 46 (permalink) Old 10-10-2014, 10:47 PM
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Hi,

The CO2 thing may be from your first post, no worries.

Tell us about your water and/or what you want or donít want apparently we are making invalid assumptions based on your questions.

If you want a chemistry class, well I am willing to tryÖ

Respectfully,
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post #15 of 46 (permalink) Old 10-10-2014, 11:04 PM Thread Starter
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Let me try being a little more specific. I have a 10g tank on my desk that is full of cryptocoryne nurii. I have grown it without using any co2 or glut. I add the basic ei chemicals in low doses and change about 50% of the water once a week. Plants grew from 1 to a full tank. Algae came and went and finally just went. For many months I added Kent Marine Coral Builder into that mix and then I stopped. Right now these plants are not looking all that well and I am wondering about adding back the coral builder or some other form of carbonates.

I don't test any of these things. I have no idea what the chemistry is.
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