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Discussion Starter · #2 ·
Somebody in another thread told me that if nitrate levels in a tank exceed 20 ppm, the tank's stocking level should be reduced or water changes should be larger or more frequent. I've gathered from experience and what I've thought to be the general concensus that something more like 80 ppm is a more reasonable "redline" when it comes to high nitrate levels being a major problem. Assuming the fish are not overfed, what do you all think?
 
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I've heard nitrate levels under 30ppm are safest long term but under 20ppm is more ideal.

Someone who knows more about this/more experience let me know if I am wrong!

~Ed
 

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I saw that part of the other thread, and I was very interested... back in the day when I knew less about maintenance than I do now, one Malawi mbuna tank had a nitrate level of over 120ppm (old test kit read lower, new one read at that! :eek: ) ... no fish died, but I did step up the water changes when I saw that and brought it back down to the 40 or so ppm level...

So the issue with Nitrate is certainly not black and white.

I also setup a Walstad no water change planted tank once... I found (even with nitrate at below 10ppm) that the TDS crept up over time, and fish started showing mild unhappy signs until I gave in and did a water change... then all was good for another 3 to 6 months...

So is it just the nitrate that is the problem? or is nitrate simply an indicator of when all pollutants from fish have built up to problem level?

Has anyone added nitrate to a tank of fish and tested "just" nitrate in a tank of cichlids?

I searched once for published papers on NitrAte and toxicity to fish... never found one. Plenty on nitrite, ammonia, etc.

I've basically come to the conclusion that high nitrates are bad... but how high is bad? I don't think we know... pity!
 

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Think of nitrates like the aquarium equivalent of dust in a house. It's an easy to read indicator of when wastes have built up and it's time to clean. Since nitrates are produced directly from the conversion of ammonia in fish waste, then there is a direct relationship between waste production and nitrate levels. Letting nitrates build up will let all the unmeasurable wastes also build up. In the case of the Walstad system, you removed your primary indicator without handling all waste products.

Fish tanks are just too small to have an entirely closed ecosystem. There will either be a build up of some products or an exhaustion of vital nutrients. Both of these are counterproductive to long-term health. Water changes remove the waste and restore the vital nutrients. Nitrate level is the best indicator we can get with our home water test kits of when the tank is degrading and needs another water change. And if nitrates are kept under 20ppm, you can be pretty sure you're doing all humanly possible to remove the waste products and restore the vital nutrients. It's just like cleaning the house when you see some dust laying about.
 

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Discussion Starter · #6 ·
Please understand the topic here. I'm not asking what ideal nitrate levels are as that is simple common sense. Obviously the lower the better. Zero , although nearly impossible without plants, would be the best. What is being asked here is:
"At what nitrate level should a tank's stocking level be reduced or water changes be done more frequnetly?" - as in when are nitrate levels so high that they can adversely affect the fish.
I would really like this poll to indicate that, and not just what people think of as "best" or what their tank's nitrate levels actually are. I don't believe that a small amount of dust in the air in my house is going to be harmful to me, but visible clouds of it are probably going to make me cough and trigger allergy symptoms. My tanks never exceed 50ppm, and that's just an estimate since the API color card goes from 40 to 60. (My results never look too much more red than the 40ppm color.)
 

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This might make an interesting read, although couldn't find the paper it refers too.

http://www.practicalfishkeeping.co.uk/pfk/pages/item.php?news=560

Edit: found it but refuse to pay for download. Here's the abstract though:

Published data on nitrate () toxicity to freshwater and marine animals are reviewed. New data on nitrate toxicity to the freshwater invertebrates Eulimnogammarus toletanus, Echinogammarus echinosetosus and Hydropsyche exocellata are also presented. The main toxic action of nitrate is due to the conversion of oxygen-carrying pigments to forms that are incapable of carrying oxygen. Nitrate toxicity to aquatic animals increases with increasing nitrate concentrations and exposure times. In contrast, nitrate toxicity may decrease with increasing body size, water salinity, and environmental adaptation. Freshwater animals appear to be more sensitive to nitrate than marine animals. A nitrate concentration of 10 mg NO3-N/l (USA federal maximum level for drinking water) can adversely affect, at least during long-term exposures, freshwater invertebrates (E. toletanus, E. echinosetosus, Cheumatopsyche pettiti, Hydropsyche occidentalis), fishes (Oncorhynchus mykiss, Oncorhynchus tshawytscha, Salmo clarki), and amphibians (Pseudacris triseriata, Rana pipiens, Rana temporaria, Bufo bufo). Safe levels below this nitrate concentration are recommended to protect sensitive freshwater animals from nitrate pollution. Furthermore, a maximum level of 2 mg NO3-N/l would be appropriate for protecting the most sensitive freshwater species. In the case of marine animals, a maximum level of 20 mg NO3-N/l may in general be acceptable. However, early developmental stages of some marine invertebrates, that are well adapted to low nitrate concentrations, may be so susceptible to nitrate as sensitive freshwater invertebrates.
 

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Discussion Starter · #8 ·
From that article:
"Just 10ppm of nitrate-nitrogen (that's a mere 3.03 ppm of nitrate) has been shown to have adverse effects on salmonids such as Oncorhynchus mykiss, Oncorhynchus tshawytscha and Salmo clarki, as well as upon a number of freshwater invertebrates and frogs."
Boy that's almost saying that keeping any fish in an aquarium is cruel. :(
 

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Cich of it all said:
Please post the link to the article. I may just break down and pay for it.
Lol.. here you go.

[/url]http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6V74-4F02KWG-B&_user=10&_coverDate=03%2F01%2F2005&_rdoc=1&_fmt=&_orig=search&_sort=d&view=c&_acct=C000050221&_version=1&_urlVersion=0&_userid=10&md5=9223511f8116baa0afab922feac45ee9[/url]
 

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I've always worked under the assumption that anything under 40ppm is fine. Mine normally never go above 30ppm, but if I'm feeling last, I know I have another few days to get around to it.
 

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you guys need to get better at Google ;)

i found the article online...

it appears that the effect of nitrate depends on age of fish and species... to be expected.

"Knepp and Arkin (1973) reported that the channel
catfish Ictalurus punctatus was able to tolerate a nitrate
concentration of 90 mg NO3-N/l without affecting their
growth and feeding activity after an exposure of 164
days"

"The first indication that relatively low concentrations
of nitrate might be harmful to fish came from Grabda
et al. (1974). They reported that fry of rainbow trout, exposed
to 5â€"6 mg NO3-N/l for several days, displayed increased
blood levels of ferrihemoglobin, alterations in
the peripheral blood and hematopoietic centres, and
liver damage."

The interesting thing is that the fry were sensitive to such low concentrations...

Keep those fry tanks spotless folks!
 

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I would expect trout species to be among the more sensitive of vertebrate freshwater fishes.
 

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Discussion Starter · #15 ·
This is getting scary! Even my lightly stocked tanks exceed 30 ppm!
Any suggestions for lowering nitrates other than larger / more frequent WC's or a reduction in stock?
Chemical filter media?
Planted refugium?
In-tank plants that Mbuna won't eat? (what are some? Vals? Java fern?)
 

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I would suggest that in high nitrate containing source water, one should take care to keep the water on the cooler side and to really aerate the water.
The other things to do would be to use floating nitrate sucking elodea, hornwort etc. in a sump tank.
Of course, the difficulty of plants as a tool for keeping nitrate low is that you have to monitor the plants for any rot or the rotting leaves can dump the nitrate back in.

All floating plants should be harvested often and any older looking stems/ leaves need to be pulled out frequently.
 

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I'm not sure why feeding and food has been left out of this equation when I think it is the most critical piece. Nitrate levels can be drastically affected by overfeeding and using foods that are not properly digested by the fish and excreted as ammonia. So conversely, feeding only what is truly required and using a highly digestible food would lead to a lower nitrate readng.

Having said that, I try to keep my tanks below 20ppm. I usually do 50% water changes weekly and this seems to keep them way down.
 

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I enjoyed reading this post, intelligent conversation by all.

I don't think that I can answer the orginal question, as I'm not a chemist. Maybe the person who told you about keepng your levels below 20ppm is. I use the powers of observation in order to understand what I should be doing in terms of nitrate reduction.

I also ran a heavily planted tank that utilized metal halide lighting and CO2 injection. Nitrate levels were zero every time I tested, no matter when I tested. Did the tank benefit from water changes? You bet it did! Every two weeks I did a 20% water change and the differences were obvious. The plants would go into serious photosynthesis. Anywhere a plant was torn, a stream of oxygen bubbles rising through the tank resulted. In addition, the fish became more active. It was a day and night difference.

It goes back to some of the earlier replies. You can't measure the dissolved organic compounds (DOC's) in the water which have a detrimental affect on the fish. Nitrates are just one of the bad guys and they are easy to measure. Can they be used as an indicator of water quality in the aquarium? Sure. But please consider that there are so many things going on in the aquarium that even noted authorities will tell you they don't have all the answers.

If you poll question had the answer "Forget focusing so much on nitrate levels and just watch the fish", I would have checked that one. :)
 

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Discussion Starter · #20 ·
If you poll question had the answer "Forget focusing so much on nitrate levels and just watch the fish", I would have checked that one.
:lol:
I just want to make sure that I'm doing the best I can to provide the most humane conditions possible for my fish. I love 'em in nearly the same way I do my cat and dogs, so I want them to live as long as possible without any adverse affects due to my negligence. :)

For the sake of my water bill, I don't want to have to do more than one 50% WC per week. I am quite satisfied with my current communities though. Maybe the new test kit I bought will show less nitrates than my old test. (although it really isn't that old - 6 months - it showed as much as 50 ppm, which because of this thread, I'm now finding to be too high.) I'll find that out tonight. If I am still getting 50 ppm, I will increase my weekly WC's to 50% (from 35-40%), and maybe reduce the stocking levels a bit. I'd prefer to stay away from the latter though, because like I said, the current mixes are working very well.
 
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