nitrate toxicity

You have asked a question that doesn't have an exact answer. It's like asking when someone will get cancer from smoking cigarettes. It depends on many factors, but even slightly detectable amounts of nitrates are toxic. Nitrates are bad for fish, plain and simple. The fact that fish are hardy enough to withstand certain amounts quite easily is an entirely different issue. (Humans seem to put up with "normal" city polution pretty well too!)

I generally keep my nitrates below 20ppm in all my tanks. Even my fish only tanks only have about 10 to 15ppm nitrate before I change water (2 weeks on my 55 gal). I would certainly say that anything above 50ppm is not good for any long term. Remember that if you place a fish that has been in crystal clear, undetectable nitrate water for a long time, then gets thrown in water with same parameters but 20ppm nitrate.....it's going to be more stressed than one slowly acclimated to 50ppm nitrate.

Hope this helps you out.
 
What sort of fish are we talking??? Not that I advocate keeping the nitrates at a certain level, but some fish are much more susceptible to nitrates than others.

Wow: 200 ppm is lethal to almost every fish!!!
 
200ppm is not lethal...Search the threads on this board for nitrates, many of your questions will be answered!

My 60 gallon Tank is over stocked and has about 100ppm I am guessing. My other 2 tanks are well below that at 20 ppm. I personally would not worry about anything less then 100ppm. There are a few fish "sensitive" to nitrates, but many wont have a problem. As for long term problems...Not sure yet. My fish are 2 years old and never had any diseases or Ich (which are caused by poor water quality). They seem to be in perfect health, with a few of them even showing breeding behaviors. I really would not worry to much about it.

Its better to have 0ppm, but dont shoot yourself if it is 100ppm. I know people that have had it at 200ppm and there fish were fine and they had them for years. Poeple worry too much about the chemicals. Do a water change once a week and dont over-feed and you will be fine.
 
<----(egg on face; was looking in shellie books and nothing else for Nitrate levels)

Good catch, Jamison.
 
Short-term versus long-term matters, as does aclimitization rate, and the particular species. There is no broad brush answer, but generally anything over 40ppm nitrate is undesirable as sensitive fish will show responses by that level.

I personally will not keep any tank above 20ppm and most of my tanks are about 10 or below
 
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