Algae and Nutrient Deficiencies - The Planted Tank Forum
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post #1 of 16 (permalink) Old 07-13-2014, 06:28 AM Thread Starter
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Algae and Nutrient Deficiencies

Here are some of my thoughts on algae's appearance in our tanks and its possible relation to nutrient deficiencies.

Observations:
There are several interesting scenarios that we are all familiar with:

1) The healthy tank, uses chemical fertilizers according to EI or PPS-Pro with very little algae in the tank.
2) Established soil tanks, very little algae.
3) Tanks with plants that don't grow well and lots of algae.

Conventional thinking used to be that it was an excess of nutrients that caused algae to appear. Lots of effort was put into eliminating excess nutrients. Frequent water changes, using carbon in our filters, phosphate scrubbers, reduced lighting, etc all reduced these "excesses" and eventually the algae disappeared as well - likely eventually succumbing to resource deficiencies. This particular method of keeping an aquarium works well with fish-only tanks, but does not work well with planted tanks. Plants develop deficiencies and die as well as the algae.

Later on the EI method allowed people to grow lots of plants quickly and over time people realized that an excess of nutrients was not the sole cause of algae in our tanks. This has been shown countless times where people often have 20+ ppm of nitrate, and 2+ ppm of phosphate along with excesses of all the other nutrients in the water column and there are no algae blooms. Under these conditions algae does not flourish so long as there are enough plants in the tank.

Diana Walstad's book - Ecology of the Planted Aquarium mentioned how many species of aquatic plants produce chemical compounds that can inhibit other species of plants. This concept made me wonder if the same could be true of plants vs. algae. After reading through obscure plant and algae journals I found out that this is in fact true as well. Plants do make allopathic chemicals that significantly reduce algae's growth. Furthermore, algae does not seem to be able to adapt to these compounds and so they remain effective even though many generations of algae are made over time.

From my botany class days where we grew mono cultures of various algae species for experiments the standard procedure was to grow algae in small glass containers which contained all the mineral nutrients that we dose in our tanks. The algae we grew developed quickly and grew healthily in these conditions. The major difference between our tanks and those test tubes is - there were no plants in the test tubes. This implies that the presences of plants influences algae's ability to grow and further supports the journal articles mentioned above.
Reference:
Miquel Lürling, Gerben van Geest, Marten Scheffer. Importance of Nutrient Competition and Allelopathic Effects in Suppression of the Green Alga Scenedesmus obliquus by the Macrophytes Chara, Elodea and Myriophyllum: Hydrobiologia Journal, February 2006, Volume 556, Issue 1, pp 209-220
http://link.springer.com/article/10....750-005-1168-3
My own research into nutrient deficiencies has uncovered many interesting relationships between nutrients and plants, along with some connections between nutrients and algae. For example, it is possible to give algae deficiencies when a tank is deprived of a nutrient.

During a discussion on what causes BBA to grow in our tanks (a lack of CO2 or an abundance of dissolved organic material in our tanks) I found several interesting articles which described how many species of algae can actually directly consume dissolved organic molecules in place of nutrients like nitrates and phosphates. In other words, algae can feed off organic molecules that plants release and dissolved partially broken down organic molecules.

Discussion:

Putting all of these seemingly unrelated facts together I think many, if not all of the algae outbreaks we observe in our tanks might be explained.

Plants suppress algae growth in a number of ways. They compete with algae by shading them out, by releasing allopathic chemicals into the water column that inhibit or kill algal species and also by growing quickly and not leaking organic molecules which algae can feed on.
Reference:

Brij Gopal, Usha Goel. Competition and allelopathy in aquatic plant communities. The Botanical Review Journal: July–September 1993, Volume 59, Issue 3, pp 155-210
http://link.springer.com/article/10....no-access=true

This is likely the reason why EI and soil tanks work so well to suppress algae. The EI method prevents plants from ever running out of any nutrient. This encourages fast growth which allows plants to shade out algae, to have plenty of excess resources to make the costly allopathic chemicals which stunt algae and also allows plants to maintain healthy intact cells which do not leak out their organic contents into the water column. These processes all combine and inhibit most algae species in our tanks from growing and taking over. Algae has to struggle to make a living and is generally confined to tiny patches near the substrate which receive enough light and which do not receive a lot of water flow (and the allopathic chemicals that are constantly being supplied in the current).

Soil tanks work in a slightly different way. After soil tanks have finished their break-in period where nutrients leach out of the soil and accumulate in the water column they become mature tanks which are extremely stable over the long term and generally have very few algae problems for many years (until the soil nutrients become depleted). Soil tanks feed the plants (via the roots) and ensure they never become deficient which in turn allows plants to shade out algae, produce expensive allopathic chemicals and maintain healthy cell walls that don't leak. However, soil tanks also tend to maintain a water column that is constantly devoid of nutrients. This nutrient deficient water column adds a fourth safeguard against algae by forcing algae to try make a living in nutrient deficient conditions on top of the other three inhibitions. Since algae does not have the ability to grow root systems it cannot move nutrients out of the soil layer through the substrate cap and into the water column area where the light that drives photosynthesis is located. These four factors combine to create an incredibly stable long term tank system that has very few algal issues. This method also has the added benefit that fertilizer delivery is automatic and does not depend on the aquarist correctly measuring out enough chemicals or remembering to fertilize their tank. This is also likely the same reason that Amano's ADA Aquasoil works so well, producing beautiful planted tanks with no algae for many years.

This idea explains why algae seems to pop up when tanks run out of nutrients. For example, when the CO2 runs out in a moderately planted tank and you see algae develop. This is not because high CO2 levels directly harm algae (algae uses CO2 as a nutrient just like plants do), but rather because the plants cannot spend as many resources on producing allopathic chemicals which normally inhibit the algae. On the other hand, if you have an extremely densely planted tank and you lose CO2 you might not see any algae - because there are enough plants to maintain a fairly high level of allopathic chemicals even though each plant is making less than it did before when CO2 was plentiful.

When a mineral nutrient runs out in a tank, like nitrogen (KNO3) for example, plants and algae begin to develop deficiencies at a fairly similar rate. Plant's develop the normal symptoms of nitrogen deficiency (decaying older leaves and smaller new growth which eventually stops growing). However, as the plant's old leaves die they release all of their proteins (high in nitrogen) and other contents into the water column where algae can directly consume it and use it for growth. This relieves the nutrient deficiency condition for the algae only. Unfortunately plants are specialists and cannot consume organic matter directly. They require nutrients to be present in mineral form (KNO3, etc) and so they remain nutrient deficient and continue to release more and more organics into the water where algae uses it. Interestingly this also seems to correspond to the location where certain species of algae will grow. Most notably BBA. BBA seems to grow on older parts of plants, at the nodes between stems where cellular connections are weaker, on filter return pipes, and on slow growing species that maintain their leaves for long periods of time. These locations are all locations where the plant cells are old, weakened and most likely leaking organics into the water column. The filter return line is loaded with organic material from the filter where bacteria have partially digested fish food and dead plant matter. In addition to the organic nutrient source plants can no longer spend resources on producing allopathic chemicals or continue to grow and shade out algae. The collapse of normal algae inhibition enables algae species that used to be suppressed by multiple processes to suddenly take off, flourish and ruin our tanks.

This idea might also explain why algae blooms are notoriously difficult to predict. After all, it is difficult to monitor our nutrient levels accurately and continually. So one line of reason suggests that the cause of "random" algae outbreaks might in fact be caused by temporary nutrient deficiencies. If plants in our tank run out of nutrients in the water column temporarily, they switch over to using up their reserve nutrient stores and start cutting corners when growing, reducing their growth rate, reducing allopathic chemical production (a luxury at this point) and preparing for starvation. This reduction of allopathic chemicals might temporarily allow opportunistic and fast growing algae species to bloom. This may also explain why we generally tend to see only a handful of algae species in our tanks compared to the thousands of species of freshwater algae that exist. The algae species we commonly get are the best species at taking advantage of sudden lapses of inhibition, blooming quickly and then going dormant until favorable conditions return.

Conclusion
Ultimately the take home message here is that if we have enough plants in our tanks, keep our plants well supplied with nutrients and never let them run out then algal issues will be minimized or completely eliminated.

Here is an image of what I just said above for all you visual people:
N2uqs and N2uqs like this.

Last edited by Zapins; 07-31-2014 at 05:50 PM. Reason: Added visual aid
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post #2 of 16 (permalink) Old 07-13-2014, 07:17 AM
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Very much appreciate the effort and content zapins.. Very useful to "non-botany" people like me to understand why of algae and what approach can be taken. .

-AqEnthusiast

4ft x 1.5ft x 1.5ft (150 L, ~40 G) | EHEIM 2217 | SunSun 110 water circulation | ADA Amazonia | 4x54w GE StarCoat 6500k T5HO 6 hrs photo | pressurised CO2 start stop one hour before photo | CO2 reactor to canister outlet | EI alternate (kno3+kh2po4+k2so4) and (csm+b) | Weekly 50% wc with Seachem Safe | MgSO4.7H2O + CaCl2.2H2O and NaHCO3 at wc to maintain kh gh at around 4 and 6
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post #3 of 16 (permalink) Old 07-13-2014, 07:19 AM
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Great writeup. After doing dirt tanks for a few years now, I've noticed that algae only appeared in the tanks during the initial startup (which is negated with frequent water changes and adding a lot of floaters and weedy stems) and when the dirt starts to lose its nutrient content after a few years. In between, plant density is heavy. Floaters clog up the surface of the tank and develop long roots. The root feeders have become weeds. Any algae such as staghorn and hair algae is nowhere to be found. BGA might be present but in small quantities, usually at the output of the filter. After a year or two, the plants start looking bad and the algae starts to take over. At that point, it's best to start over with some fresh dirt.

As for the BBA being caused by organics, I read all 40 something pages of that thread on APC which talked about how dissolved organics in the water was utilized by algae. I believe it's true from what I've seen. Slow growing plants with damaged leaves become bba magnets. Anubias, ferns, and slower growing crypts are the most susceptible in my tanks. These are in low tech, non-co2 injected tanks btw. The bba never shows up on the newer leaves. Changing the water more frequently in larger volumes helped prevent new outbreaks of bba. But the old tufts would still remain. The best course of action at that point was to trim any of the heavily infested leaves. There's no point in using H2O2 to spot dose when you can just let the plant grow new leaves. The 1-2 punch works just fine IME but if the plants aren't growing well, the bba is gonna come back unless you improve your plant growth. Just my two cents.

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post #4 of 16 (permalink) Old 07-13-2014, 07:45 AM
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Good conclusion.

Allelopathy might be an issue of "here's the conclusion, let's see what facts we can find to support them."
It be unlikely true in flowing systems as the chemicals are quickly and immediately washed away, and that's the lion's share of the systems in springs in Florida. How does a plant know how large the area is and what the water flow is and how much to produce?
How is it that we see the same observations in some 400+ species of aquatic plants? Surly, all 400 different wide ranging species do not all produce some secret bullet chemical?
Those odds are well over Billion's to one.

Ole beats the rest of that argument to death:
http://www.bio-web.dk/ole_pedersen/p..._2002_15_7.pdf

Water changes are a very easy way to remove allelopathic chemicals.
If that's not good enough, they no water changes should kill off any algae, but clearly that does not work, the opposite tends to be more true for cO2 enriched systems.
And you can use activated carbon which is a standard control for allelopathy research studies in plant ecology. Plenty of hobbyists have used AC in planted tanks for years, no one has noticed any increase in algae with it's use. To accept the hypothesis, you would almost need to have most folks see algae blooms.
Try it and see for yourself


Then there's whole issue of why cannot algae use the same chemicals to fight each other and against plants?
Chara does it it might seem.

I fully agree with the main point in the discussion, but with BBA and organics, why does it NOT grow in my non CO2 tanks? Consistently and without fail?
those tanks get no water changes except once every few months, lots of organic build up.

Excel dosing, well, it's a selective biocide. Still, works best when using a non CO2 gas enrichment method to retard algae.

You might suggest the rates of organic loading are more a factor, rather than just the concentration perhaps. Organic loading can come from many sources and has many types.

Ultimately, I think for hobbyists, they can run around and chase all this stuff, or stick to the basic and focus on plants, and good general aquarium care.

I'd not stick my neck out on the allelopathy issue though. there's just way too many cases that show it does not impact planted tanks.

I think there's some link with bacteria in the sediment and the roots and shoots. Might be simply a nice established community partnership with plants, that does not happen with algae.

Tanks never seem to do well till the roots grow in well, but..........if the root do not grow in well, you have a plant growth issue also, so..that's a toughie also.

But after the roots grow in and the plants bloom out some, then the tank is pretty tough.Frequent water changes in the 1-2 month phase dramatic helps establishment without algae for CO2 enrichment. This runs counter to the allelopathic hypothesis and what Walstad suggest for non CO2 soil based tanks with no water changes. How does the plant know if it's in a small puddle or a large lake? Say Lake Tahoe, or the Fall river, the CA Delta(FW tidal) or a small 1/4 acre pond? I've seen Eurasian Milfoil growing very well in all these places. That's a massive difference in habitat. Same for P crispus. Dang weeds.

Still, you need not a PhD to be a good farmer or aquascaper
Elbow grease likely will serve you much better.



Tanks! and Tanks! like this.

Regards,
Tom Barr
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post #5 of 16 (permalink) Old 07-13-2014, 08:22 AM
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An excellent explanation about the main causes of algae outbreaks in planted tanks. Great read, nice write-up, and good conclusions. Now I better make sure I fertilize a little more frequently than ever, since I did increase my plant loads quite a bit as of late in some of my planted tanks. Grateful for the insightful information, Zapins.

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post #6 of 16 (permalink) Old 07-13-2014, 09:27 AM
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This is great info for me here with perfect timing....i have just started to see some sort of beard algea on some of my plants and tiny green dots on the glass so i did a water change yesterday ,i upped my co2 slightly an im still trying to find the sweet spot for that....i use profito fertilizer as directed once a week but here is where im unsure .

after i made the 30% water change should i start my weekly dose of profito on the day or just wait for the day i normally add....

iv just removed nutrients which could actually slow down my plant growth and might help the algae rather than put it under pressure

last week i reduced my lighting down to 6 hours too from 9hours...
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post #7 of 16 (permalink) Old 07-13-2014, 02:36 PM
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Very nice article Zapins. I like the fact that you're willing to question the current comprehension of the ecology of the planted tank. In particular, allelopathy.

The debate over allelopathy in the planted tank seems to be quite polarized in my opinion. It's either the "missing link" for algae control or it has no effect whatsoever. My belief is the answer lies somewhere in the middle.

Clearly allelopathy exists. However, allelopathy is a rather general term used to describe a large array of compounds and effects.

I had a tank with a thick carpet of dwarf hairgrass. I noticed a couple of stray crypts had taken root there. I essentially ignored this more out of laziness. After several weeks I quit ignoring it. The crypts in the hairgrass would not grow. They simply existed. On the other side of the tank the same plants grew like weeds. Allelopathy? It seems so. Eleocharis secrete allelopthic compounds at the roots. This isn't algae but it does suggest allelopathy plays a role in the planted tank.

I do question the idea that allelopathy plays no role on algae in the planted tank due to factors such as dilution, water changes or removal via AC. This argument assume that allelopathy can only occur in the water column. I do agree that the allelopathic compounds would have no effect in the water column as a result of these factors. However, there are concentration gradients that need to be considered.

Effluents affect ecology of rivers at a much higher rate around the discharge area. Where as miles down stream the ecology seems unaffected. If we scale that same effect down why couldn't the allelopathic compounds have an effect on algae at the site of discharge? It would seem an effective defense against algae attaching to plants blocking valuable resources. This mechanism would be unaffected by the size of the body of water and to a lesser degree the velocity of current. Conjecture? Absolutely! Yet it is a possibility.
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post #8 of 16 (permalink) Old 07-14-2014, 04:04 AM
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From a practical standpoint what would you do differently if allelopathy was occurring as a weapon plants use against algae, versus if it isn't occurring? And, what experiment, short of removing big organic molecules with AC, would you do to demonstrate the presence of allelopathy as a plant weapon vs. algae? If you would do nothing different, and if you can't find any experiment to demonstrate allelopathy, does it matter whether allelopathy exists as a plant weapon vs algae? If the answer is that it doesn't matter, then it becomes irrelevant.

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post #9 of 16 (permalink) Old 07-14-2014, 04:15 AM
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We often talk about soil tanks or nutritious substrate tanks as being those with low nutrient levels in the water. I'm not a chemist, nor am I a botanist, so I lack some basic information. Is it true that plants can use nutrients only if those nutrients are ions? Molecules which don't release ions into the water when they are in water would therefore not be available as food to the plants? But, ions in water are always equalizing concentrations throughout a body of water, "flowing" from high concentration areas to low concentration areas. So, is it possible to have a high available nutrient substrate and low available nutrient water in the same tank? Doesn't that make it obvious that available nutrients in the substrate must also be available in the water at near the same concentrations?

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post #10 of 16 (permalink) Old 07-14-2014, 11:44 PM
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I honestly don't think the average hobbyist can determine whether allelopathic algae control exists or to what degree. The current techniques do work. Is it because of this or that? That's the question.

Humanity seems to be one part survival and two parts curiosity IMO. Does it really matter what happens to matter when it enters a black hole? Yet we spend enormous amounts of money to research curiosities such as this. Sometimes, we can directly use the information we discover. Other times we can't. However, we can build on what we've learned to discover things that are useful in everyday use. I think it's simply human nature to ask why. We could continue to do XYZ and have positive results. Yet without full understanding we will never know if the positive results we seek are the maximum we can obtain.

I'm not a chemist or botanist either. However, I would think the nutrient concentration in the substrate would be higher than the water column. The ions in question have to be close to one another to react. Without adequate turn over those ionic concentrations would not equalize. It's much like a smokers lungs. The volume of air in the lungs are normal yet the gaseous content in the blood is blocked from various barriers. So basically, the two polarized ions would be less likely to meet in the substrate versus in the water column. At least that's my over simplified and ignorant view on the process.
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post #11 of 16 (permalink) Old 07-15-2014, 01:40 AM
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As I see it, when a substance dissolves in water that substance's molecules separate into ions, equal numbers of cations and anions. Those don't recombine in the water, but circulate in the water freely. In an underwater substrate, the same thing happens except that if the substrate has an appreciable cation exchange capacity, the cations are held in one place by the substrate, with the anions circulating in close proximity. But, a low CEC substrate can't grab and hold the cations, so they can freely move into the water that isn't in the substrate. Conversely, dissolved fertilizers in the water also consist of cations and anions, which freely migrate into the substrate water. That leads me to believe that a nutritious substrate, ADA Aquasoil, for example, causes the tank water to also be loaded with fertilizer.

I agree that even though we can't use our knowledge about allelopathy, for example, it is still interesting to gain that knowledge, and possibly apply it in a new way.

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post #12 of 16 (permalink) Old 07-15-2014, 01:28 PM
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Quote:
Originally Posted by Hoppy View Post
Is it true that plants can use nutrients only if those nutrients are ions?
That's my understanding as well.

The amount of nutrient leaching would vary based on the substrate type. Rich organic substrates, such as organic soil, would have a much higher nutrient concentration than the water column. Sure there is some leaching yet the bulk of nutrients will remain in the substrate. Organic substrates have a high CEC which means cations, such as NH4, will be attracted and "bound" to the substrate.

Inert substrates could theoretically equalize if there was sufficient flow through the substrate. However, most people don't use UGF. If substrate fertilizers are used in an inert substrate the concentration would still be higher than the water column. Again there is some leaching that occurs but not enough to equalize nutrient levels.

Many people see an algae outbreak when uprooting a lot of plants or rescaping. Ammonia levels are greater in the substrate of an established aquarium. So disturbing the substrate releases ammonia leading to algae.

So to have high levels of nutrients in the water column from leaching, the substrate would need to be very rich. Much more so than the water column. That's basically how I see it. Right or wrong.
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post #13 of 16 (permalink) Old 07-15-2014, 03:45 PM
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Quote:
Originally Posted by Zorfox View Post
That's my understanding as well.

The amount of nutrient leaching would vary based on the substrate type. Rich organic substrates, such as organic soil, would have a much higher nutrient concentration than the water column. Sure there is some leaching yet the bulk of nutrients will remain in the substrate. Organic substrates have a high CEC which means cations, such as NH4, will be attracted and "bound" to the substrate.
I agree that high CEC substrates would hold nutrients, thus limit the leakage of nutrients into the water column.
Quote:

Inert substrates could theoretically equalize if there was sufficient flow through the substrate. However, most people don't use UGF. If substrate fertilizers are used in an inert substrate the concentration would still be higher than the water column. Again there is some leaching that occurs but not enough to equalize nutrient levels.
Ions in water will always migrate to areas of lesser concentration. This is an example of entropy, where everything tries to achieve zero differences in any attribute. No water circulation is needed, since ions are always moving around in the water.
Quote:

Many people see an algae outbreak when uprooting a lot of plants or rescaping. Ammonia levels are greater in the substrate of an established aquarium. So disturbing the substrate releases ammonia leading to algae.
Agreed, but I don't know what mechanism acts to release the ammonia.
Quote:

So to have high levels of nutrients in the water column from leaching, the substrate would need to be very rich. Much more so than the water column. That's basically how I see it. Right or wrong.
I don't think that is correct. Nature always works to make everything equalized. That is the basis of entropy.

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post #14 of 16 (permalink) Old 07-15-2014, 04:37 PM Thread Starter
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I'm glad you are discussing this idea. I have enjoyed reading your comments. Unforutnately I have been extremely busy studying since I posted this. I'm doing gross anatomy in my first year of medical school so my time is limited. I will reply briefly now, but will try reply more fully soon.

Hoppy - yes, for nutrients to be absorbed they must be in ion form. This is because only ions are soluble in water (polarity of the ion allows it to dissolve in the weakly polar water). The dissolved nutrients are used by the plants.

However, there is definitely a pretty hard and fast barrier to nutrients in soil systems. The substrate cap blocks a lot of nutrients from reaching the water column. This is because although nutrients dissolve into the water in the soil layer this water does not exchange with water column water in huge amounts. The exchange of water between the two layers is therefore limited. This can be verified by test kits if you like on mature soil tanks, but also by the fact that ephiphytic plants like anubias/ferns often develop deficiencies when grown in soil tanks when they are not directly planted in the soil layer.

On top of this, a lot of nutrients in the soil layer are produced over time by decomposition. They are locked up in organic molecules that are not as soluble as salts like KNO3, KH2PO4. Most of these highly soluble salts are flushed out of the soil layer within the first few weeks of setting a tank up, this is also why you must add potassium to aquasoil after a few weeks (potassium salts are very soluble). Then over the next several years most of the nutrients the plants have access to come from decomposition or from the CEC properties of the soil. So the water column of a mature soil tank is deficient of nutrients compared with an EI or PPS based tank. Remember, it only takes a total lack of 1 nutrient to stunt algae or plant growth and cause the organism to die eventually. Minerals like Ca/Mg are not deficient in the water column, but N and P and probably a few others are which is enough to make growing conditions unfavorable for algae or plants that have no access to the soil.
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post #15 of 16 (permalink) Old 07-15-2014, 04:57 PM
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Quote:
Originally Posted by Zapins View Post
I'm glad you are discussing this idea. I have enjoyed reading your comments. Unforutnately I have been extremely busy studying since I posted this. I'm doing gross anatomy in my first year of medical school so my time is limited. I will reply briefly now, but will try reply more fully soon.

Hoppy - yes, for nutrients to be absorbed they must be in ion form. This is because only ions are soluble in water (polarity of the ion allows it to dissolve in the weakly polar water). The dissolved nutrients are used by the plants.

However, there is definitely a pretty hard and fast barrier to nutrients in soil systems. The substrate cap blocks a lot of nutrients from reaching the water column. This is because although nutrients dissolve into the water in the soil layer this water does not exchange with water column water in huge amounts. The exchange of water between the two layers is therefore limited. This can be verified by test kits if you like on mature soil tanks, but also by the fact that ephiphytic plants like anubias/ferns often develop deficiencies when grown in soil tanks when they are not directly planted in the soil layer.

On top of this, a lot of nutrients in the soil layer are produced over time by decomposition. They are locked up in organic molecules that are not as soluble as salts like KNO3, KH2PO4. Most of these highly soluble salts are flushed out of the soil layer within the first few weeks of setting a tank up, this is also why you must add potassium to aquasoil after a few weeks (potassium salts are very soluble). Then over the next several years most of the nutrients the plants have access to come from decomposition or from the CEC properties of the soil. So the water column of a mature soil tank is deficient of nutrients compared with an EI or PPS based tank. Remember, it only takes a total lack of 1 nutrient to stunt algae or plant growth and cause the organism to die eventually. Minerals like Ca/Mg are not deficient in the water column, but N and P and probably a few others are which is enough to make growing conditions unfavorable for algae or plants that have no access to the soil.
Interesting! Thank you. The Devil is in the details

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