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Discussion Starter · #1 ·
Hello

Before a few months I have set up a low tech aquarium according to Diana Walstad method.

Last week I introduced Limnobium laevigatum to reduce organic matter in the water.

During one week the mass of the plant was tripled and after one week new leaves started to be yellow with signs of iron deficiency.

My question applies not only to this particular plant, but generally to every floating and epiphyte plant that can only take iron from water column.

As I know fish feces cannot produce ferrous iron that is easily accessible to the plants.

Question: Is it necessary to fertilize low tech aquarium with chelated microelements if non rooted plants are used?

I would like to avoid fertilizers as far as it is possible.

I have searched internet to find an answer to this question but without luck.


Regards
Wojtek
 

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Welcome to APC! That's an interesting question, too. I'm still thinking about the question - nothing to share yet.
 

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Everybody's tank is different but I've seen nutrient deficiency in low tech tank. I've dose nutrients into them.
 

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I think the answer is that no it isn't necessary to fertilize the plants in a low tech tank. It is very likely that it will be beneficial if you do dose NPK and trace elements, but not essential. If you have plants that are generally thought of as obnoxious weeds you probably won't want the benefits of dosing them, but there are many other plants that can grow at an acceptable rate in a low tech tank and grow at a more acceptable rate if you dose NPK and trace elements. This assumes that your light intensity is adequate for those plants.
 

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Discussion Starter · #5 · (Edited)
Thank you for the answers

Of course I don't want to fertilize a plant which grows to fast.

I would like to understand more technically what chemical reactions occur in my aquarium.

Let's assume a situation that all previously available iron is depleted from the water column because of Limnobium. Hipothetically I wont make any water changes and only feed my fish. Is it possible in this case that non rooted plants get after some time new FE2+ ions from the water column from fish poop? Is it possible that new Fe3+ ions from fish food are reduced to Fe2+ which is accessible for plants?

This question is important for my situation. I have a microsorum and Limnobium. I don't want to starve microsorum. I prefer to reduce periodically amount of Limnobium and increase fish load to produce more nutrients including iron. I would make it of course only if it would be a reasonable action.

@Hoppy I have found your entries in the following thread:
https://www.aquaticplantcentral.com/forumapc/algae/143287-algae-iron.html

You wrote
A high light tank, with CO2 being added, will cause the plants to grow too fast for the substrate nutrients to supply all that the plants need. So, we dose the water column to keep them growing. This process works somewhat different from lower light tanks. But, the effect of iron in the water, with intense lighting causing iron photoreduction, should be the same. I can't reconcile that with Ms Walstad's theory, knowing that many people do have high light, CO2 dosed tanks with iron being dosed in the water, and which don't have serious algae problems. But, there has to be a way to explain it. Similarly, why does a heavily planted tank discourage algae growth? It cannot just be magic. The physical reactions, and the science behind them, should be consistent whatever light intensity or fertilizing method or substrate we use.
Do we have iron photoreduction or something else in low tech tank, that cause Fe+3 -> Fe+2 reduction?

FE+3 is not accessible for plants at all or with more effort?
 

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I was going to try to experiment with a 10 gallon tank, split into two 5 gallon compartments, but I found that I had forgotten too much that I knew, and had to drop the idea. That tank now rests in my closet. I'm in over my head with this subject!!
 

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Discussion Starter · #7 ·
Hello Hoppy

No problem. I have found something interesting to this problem.

https://www.tandfonline.com/doi/abs/10.1080/01904168609363478?journalCode=lpla20

Findings of the present investigation cast doubt upon the validity of the earlier conclusion and support the belief that both Fe(III) and Fe(II) ions can be absorbed. Demands upon the plant are correspondingly less and, during non‐stress periods, might be negligibly small. During non‐stress periods, rate of absorption of Fe(III) might be adequate to meet plant requirements.
regards from Poland
Wojtek
 

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Question: Is it necessary to fertilize low tech aquarium with chelated microelements if non rooted plants are used?
Hi @szkotkr

Some nutrients will leach from the substrate/sediment, if present. But, which nutrients and whether or not they will be sufficient to adequately fertilize epiphytes and floating plants is the $64,000 question. I would perform water tests for iron, nitrate and phosphate in the first instance. I doubt that the tank water is deficient in calcium, magnesium and potassium but these can all be tested, if necessary. I see that you're in Poland. I'm in Europe and I use JBL test kits.

Yorkie
 

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Do we have iron photoreduction or something else in low tech tank, that cause Fe+3 -> Fe+2 reduction?

FE+3 is not accessible for plants at all or with more effort?
I doubt photoreduction of Fe3 can occur under artificial light in low or high tech due to absence of UV to energize the reduction.

Fe3 is unavailable to plants in the water column because it is insoluble unless it is made soluble in chelated form.
 
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