# [Wet Thumb Forum]-Nitrates



## aquabillpers (Apr 13, 2006)

I set up a low light, soil-based tank in August.
The six species of plants in it are growing and reproducing, requiring pruning every three or four weeks. Even with that, it is jungle-like. It's perhaps my most successfull tank ever.

The nitrate level in it is 2 - 3 ppm (three kits). From what I've read, nitrate levels of 5 - 10 ppm seem to be preferable. 

The soil used in the tank is low organic subsoil. Since the plants are doing so well, I am wondering if they are getting the nitrates from the soil or are they making do with what the biological processes in the tank generate?
Or are they slowly starving?

Thanks.

Bill


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## aquabillpers (Apr 13, 2006)

I set up a low light, soil-based tank in August.
The six species of plants in it are growing and reproducing, requiring pruning every three or four weeks. Even with that, it is jungle-like. It's perhaps my most successfull tank ever.

The nitrate level in it is 2 - 3 ppm (three kits). From what I've read, nitrate levels of 5 - 10 ppm seem to be preferable. 

The soil used in the tank is low organic subsoil. Since the plants are doing so well, I am wondering if they are getting the nitrates from the soil or are they making do with what the biological processes in the tank generate?
Or are they slowly starving?

Thanks.

Bill


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## DataGuru (Mar 11, 2005)

It doesn't sound to me like they're deprived of anything if everything is growing and need pruning. So what kind of fish load do you have in the tank?

According to Diane, the plants actually prefer ammonia over nitrAte cuz they don't have to work to suck ammonia up. It just diffuses in. What I think is happening, is that the plants are using most of the ammonia rather than the biofilter bacteria and it gets converted into plant mass rather than into nitrAte.

Got any pics?


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## aquabillpers (Apr 13, 2006)

Betty,

Thanks for your response to my question.

The tank was set uo with tap water from a deep well that has about 10 ppm of nitrates.

The fish population consists of an unknown <g> number of guppies, mainly fry, the offspring of 
some feeders that I bought. I'm sure that they are supplying some ammonia.

Are You saying that the substrate is not supplying nitrates and what there is coming from biological activity in the tank plus what was in there from the water?

Bill


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## Margolis (Sep 22, 2004)

nitrates are the end result of the biological breakdown of fish wastes. If you want more nitrate, feed your fish more


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## DataGuru (Mar 11, 2005)

No, I was referring to nitrAtes in the water column. I'd have to go read Diane's book again to be 100% sure on your substrate question, but I'd bet they're able to suck up nitrogen from the soil via their roots.


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## aquabillpers (Apr 13, 2006)

Margolis,

The tank has 20 to 40 fish in it, mainly guppy fry and juveniles. I don't know if they would
would provide enough nitrates (and other nutrients) to feed a heavily planted tank. 

Which raises another question: How many well fed fish are required to fertilize a heavily planted tank?

Bill


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## aquabillpers (Apr 13, 2006)

Betty,

I thought that they would get nitrates for the soil too, but I couldn't find anything in Diane's book to support that. And as I think about it, if the substrate is subsoil, it lacks organics and might not have much in there anyway.

I checked the nitrates a few hours ago. They were still around 2, and the phosphates were almost nonexistent. In poking around in hidden areas of the tank, I noted that the hygrophila was not as good as it had been and there was algae on some of the hornwort.

So I added some KN03 and some Fleet Enema for the phosphate, biting my lip as I did. And we'll see.

Bill


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## dwalstad (Apr 14, 2006)

I'll be out-of-touch until January 5, but it looks like the other members are doing a good job of answering your questions.

Nitrates are mostly in the water. Because nitrates have a negative charge, they don't stick to soil particles, which are also negatively charged.


2-3 ppm nitrates should be plenty. It means that your plants are taking up ammonia nitrogen, and when they've consumed this, they're using some of the nitrates. Thus, the water is going from 10 ppm down to 2 ppm. 

I'd be careful with adding fertilizers to the water. You're already starting to get some algae. I'd feed fish more or try adding a few small plant tabs to the substrate.


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## aquabillpers (Apr 13, 2006)

This is an update to my experience with the natural tank that seemed to be eating itself into an early takedown.

On December 22 I found nitrates to be at 1 ppm and phosphates, at .1. Both of these were well under what some people say are appropriate levels.

Dosing upped those levels to 25 and .9, but on Januart 4, about two weeks later, they were down to 6 and .1. The rooted plants were doing fine, but the stem plants were suffering, The hygrophila polysperma, once growing like the weed that is is, now had lost most of its lower leaves and displayed long internodal spaces, classic symptoms of nitrate deficiency. So I dosed again.

As I stated in my orignal post, I have 40 to 60 guppies, mainly fry, in this tank. They are well fed and grow at a normal rate (the ones I can't catch, anyway) but apparently there are just not enough of them to fertilize the plants.

For balance, I have a 29 gallon tank soil-based tank with about one inch of larger fish per gallon. The nitrate and phosphate levels in it are not a problem, although the plant growth isn't a vibrant as it was in the 20 gallon.

Bill


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## dwalstad (Apr 14, 2006)

> quote:
> 
> Originally posted by Billpers:
> This is an update to my experience with the natural tank that seemed to be eating itself into an early takedown.
> ...


Dear Bill,

I don't know where you read that 1 ppm nitrates and 0.1 phosphates were low levels, but it wasn't in my book! Or in this Forum! If we're talking about a soil-based tank without CO2 injection, then these levels are fine; in fact, they are highly desirable.

As I wrote in my book, if you think your plants need more nutrients, then just add a little more fishfood to the tank. You don't need to increase the fish load, because bacteria will do the same thing as fish-- convert fishfood to the nutrients plants can use.

Adding inorganic chemicals like potassium nitrate and magnesium sulfate can create serious problems for fish and plants. If you want to add inorganic chemicals like these to your "Natural" tank, then you need to post your questions in another discussion forum.

It sounds to me like you had a good, low-maintenance tank going and are now spoiling it by adding fertilizers. Stem plants like Hygrophila, which can't use bicarbonates, often need more CO2 than many rooted plants, which can use bicarbonates. So your limiting nutrient is probably CO2-- not nitrates or phosphates.

I would relax and consider the tank a success if you have good growth of most plants, healthy fish, and no algae problems.


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## Maurici (May 31, 2004)

Dear Bilpers,
I think that is possible that you don't have a nitrates problem, the fishes you have would be enough efficient to add the ammonia required for the plants. Perhaps is a Fe problem (I discard K and P if you added KNO3 and phosphorus). Nevertheless, be careful adding Fe if you have an algal invasion exploiting the actual disequilibrium.
Dear Diana, you posted:


> quote:
> 
> Adding inorganic chemicals like potassium nitrate and magnesium sulfate can create serious problems for fish and plants.


 Can you explain why KNO3 is not good? is the source of K available from water enough for the plants? perhaps this indispensable content is provided by regular and often water changes, is it?
Thanks.
Maurici.


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## aquabillpers (Apr 13, 2006)

Hello,

Thanks, Diane, Betty, and the other folks who responded to my questions.

I think the main cause of my problem - the dying off of the stem plants - was caused by insufficient nutrients in the water column. I'm sure that Diane is correct when she says that levels of 1.0 of NO3 and .1 of PO4 are adequate in this kind of tank, but twice my NO3 levels dropped from 10 to 1 in about 2 weeks, and the difference between 1 and zero is small. And the hygro had the symptoms of nitrate deficiency.

But the more important question is, "Why?" I think the answer to that is that the fish, mainly small guppy fry, and other organisms just didn't eat enough to produce the needed nutrients. 

I don't understand how low co2 could exist in that tank. The CO2 level should stay at atmospheric levels, about 3 ppm, even if there was a lot of surface disturbance, which there wasn't in this case. But maybe I'm missing something.

I am going to set up a new 20 gallon with a subsoil/dash of peat/mulm substrate and stock it with about 15 near-adult platies who happen to be handy. They will be well fed. It will be planted with root plants only. And I'm sure that it will turn out just fine.

Bill


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## dwalstad (Apr 14, 2006)

[/QUOTE] Can you explain why KNO3 is not good? is the source of K available from water enough for the plants? perhaps this indispensable content is provided by regular and often water changes, is it?
Thanks.
Maurici.[/QUOTE]

Adding KNO3 is probably not going to cause problems in most setups. But it could. Nitrates can diffuse into the substrate and be converted (under mild anaerobic conditions) to nitrites, which are very toxic to fish.

This process ("nitrate respiration" is described in my book on page 65). This is a very common process carried out by lots of ordinary bacteria. Because my tanks tend to accumulate nitrates, occasionally I've had nitrite problems. I believe it is due to nitrite respiration.

In my tanks, most KNO3 is provided by the breakdown of fishfood, not water changes.

I calculated (see my book, page 89) that the fishfood input into my 50 gal tank provided 10X the nitrogen that my plants need.

In general, most aquariums have an excess of nitrogen, not a deficiency.

A slight case can be made for adding K, especially in softwater, which often is K deficient (my book page 86). Also, I found that fishfood doesn't provides K as generously as N. However, if you must add K, my advice would be to add it as KCl, not KNO3.


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## dwalstad (Apr 14, 2006)

> quote:
> 
> Originally posted by Billpers:
> I think the main cause of my problem - the dying off of the stem plants - was caused by insufficient nutrients in the water column. I'm sure that Diane is correct when she says that levels of 1.0 of NO3 and .1 of PO4 are adequate in this kind of tank, but twice my NO3 levels dropped from 10 to 1 in about 2 weeks, and the difference between 1 and zero is small. And the hygro had the symptoms of nitrate deficiency.
> ...


Dear Bill,

You're missing a critical #. Water in equilibrium with air contains only about 0.5 ppm CO2 (my book page 100). This is not enough for most plants; plant photosynthesis often draws CO2 levels down to zero. Many rooted plants can bypass the problem by using bicarbonates, but stem plants can't, so they are at a disadvantage. Hobbyists who fertilize with CO2 often maintain CO2 in the 10 to 30 ppm range; they report stimulated plant growth and the ability to keep stem plants happy.

As to the nitrates quickly going from 10 to 1. This could be due to denitrification, which converts nitrates to nitrogen gas NOT plant uptake. I suspect that your plants are getting adequate N (released as ammonia N via the fishfood input). You would practically have to starve those guppies to make your tank N deficient!

However, we can waste time speculating forever and get nowhere. Find out for yourself. Add a little KNO3 and see if your stem plants perk up. We all know that plants with N deficiency (yellow leaves) will "green up" within days of getting nitrogen-containing fertilizers. If your stem plants turn green and start growing, you will know that the problem was either a K deficiency or an N deficiency.


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## Maurici (May 31, 2004)

Dear Diana,
I think that problem can be the poor aeration of deeper zones of the substrate and the non balanced NO3 produced and used for the plants, I agree that the matter for concern with nitrates is often not a deficiency case rather than an excess. But my sound is about K, really scarce on many waters for the planted aquarium demands. Could KCl be an additional problem giving salt formation (NaCL)on hard waters?, then the remedy is worst than illness. I'm confident that if you have a good turnover of nitrates it is no great matter the KNO3 addition.


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## dwalstad (Apr 14, 2006)

As a general rule, I don't recommend inorganic fertilizers like KNO3. I recommend fishfood as the safest, easiest, and cheapest way for hobbyists to provide nutrients to plants. That's how I maintain my tanks and plants do fine.

However, I always encourage hobbyists to experiment and find out for themselves. Try the KNO3 and see what happens.


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## Maurici (May 31, 2004)

Dear Diana,
Your success and knowledge about marvelous planted tanks is a quasi Utopian goal for many of us. I'm one who is fascinated for the simplicity of the plant care you follow, but I would like to explain you my interest making concrete questions like these. It is only motivated by the difficulty of distinguish a decay of conditions due to an unbalanced habitat and the normal dynamics of the cultivated plants. Many times increasing the knowledge viewing and reading about symptoms of nutrient problems and contradictory messages of cultivators about how to fight them provide me of something like a catastrophic sensibility about the future of my plants, Is better to look hard to find the reason of yellow leaves on my Echinodorus or to let "natural" death of some species convinced in that the conditions offered by my tank are not quite good for them? Is the life so complex that not permit cohabitation of many taxa we want to grow in the same tank, and our efforts in this sense are obligate failures?
Kind regards.
Maurici


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## aquabillpers (Apr 13, 2006)

Diana said:



> quote:
> 
> However, we can waste time speculating forever and get nowhere. Find out for yourself. Add a little KNO3 and see if your stem plants perk up. We all know that plants with N deficiency (yellow leaves) will "green up" within days of getting nitrogen-containing fertilizers. If your stem plants turn green and start growing, you will know that the problem was either a K deficiency or an N deficiency.


I did it. I raised the nitrates to 35 ppm (yes, I overshot badly) and the phosphates to
.7 ppm. Ten days later, the hygrophila has resumed its healthy growth and the symptoms of nitrate deficiency have vanished.

But - in 10 days the nitrates have dropped to 7 ppm and the phosphates to .2. That tank just doesn't produce enough plant nutrients with its present population of small guppies. I will add some platys and some rams and see what happens.

I noticed that a dark algae is growing on older leaves of some of the plants. There isn't enough to concern me much now, but I'll keep an eye on it. Presumably when the tank gets back to a natural balance it will go away, more or less.

Bill


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## mrmag (Jan 12, 2005)

Perhaps we could start a discussion on best techniques for raising NO3 with fish foods.

What do we look for when buying a good flake if we want to increase NO3?

I am in the same situation as Bill

Also, to play devil's advocate... Can overfeeding fish cause health problems? Also... does my largest cardinal tetra ever stop eating? (so far, No)

mrm


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## mrmag (Jan 12, 2005)

Bill

Does your tank have heavy biological filtration? This might explain your NO3 loss as Diana mentioned (denitrification).

Perhaps worth some experimenting. Many people here do not use biological filtration, just very basic mechanical. It is possible your filter is stealing nitrates from your plants.


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## aquabillpers (Apr 13, 2006)

Mrm,

Thanks for responding.

My tank has no biological filtration except for that which is provided by the plants, if that is indeed that.

I do have a small Aquaclear HOB, the smallest, for circulation, and it does have some floss in it, but I'm sure that isn't the cause of the nitrate drop.

Actually, since the number of guppies has increased and since they are getting more food, the nitrates seem to be dropping more slowly. I haven't added any for six weeks, but the level has dropped from 35 to 10 during that period. The phosphates drop faster, roughly 1 ppm per month.

I think a combination of a lot of fish and a lot of fish food will take care of any nitrate problem, but I don't know about the phosphates.
I feed this tank mainly Tetramin flakes. They are 1 percent "phosphorous." I don't know how that translates into phosphates. Maybe someone else does.

I have another low light, soil substrate aquarium that maintains nutrient levels quite well without augmentation. It has a larger fish population, and the plants aren't growing as rapidly. It gets Tetramin and a lot of Grindal worms.

The more I think I learn, the less I know I know.

Bill


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## mrmag (Jan 12, 2005)

Sounds like the tank is starting to stabilise a bit. I have noticed that a lot of flake foods are all low phosphorus, claiming "won't pollute water," etc. 

I'd like to find some resources on nutrient analysis of different types of food. I am imagining feeding your fish different foods based on observed signs of limiting resources for plants. 

Another problem I have found is that heavy feeding makes my Otos very lazy (who wants to eat algae with all that food lying around?). As a result, they neglect their housekeeping chores and the plants start to get choked w/ algae.


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## dwalstad (Apr 14, 2006)

> I'd like to find some resources on nutrient analysis of different types of food. I am imagining feeding your fish different foods based on observed signs of limiting resources for plants.
> QUOTE]
> 
> On page 79 of my book is a table summarizing several different analysees of four different fishfoods. The P content was about 15 grams/kilogram dry weight (range was 9 to 23).
> ...


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