Biology question on ammonia/nitrates

[HoopsGuru]

I've been doing some reading on my own, mostly researching the effects of nitrate levels on fish. There obviously aren't many actual studies available...at least not to the public. I have noticed though that various fish have very various levels of tolerance with ammonia. Is it also safe then to assume that fish (both fresh and saltwater) have an equal variation in tolerance to nitrates (as in that nitrates are more toxic to others). Or, is it more likely explained that nitrates are equally toxic to all fish, just some exhibit outward signs of distress more easily (HITH, HLLE). An example of this is that I took over maintenance of a tank in an office where the tangs have HLLE but the chromis, hawkfish, and engineer goby do not and it made me ponder this question.

Obviously, the goal is to keep nitrates as low as possible for all fish...that is not debateable or of interest to me. Once again, from a biological standpoint, do some fish process nitrates better and thus not show these afflictions in much the same way some fish handle ammonia differently?

 

[seapug]

In general fish are quite tolerant of elevated levels of nitrate, but not ammonia. Ammonia is the most toxic form, then nitrite, then nitrate. That said, tolerance for nitrate does vary between species of fish.

The hlle you are seeing in the tangs is most likely related to improper diet, not nitrate.

 

[HoopsGuru]

Thanks for the response, I understand the general relevance of the nitrogen cycle. My question is a bit deeper into the biology of ammonia and/or nitrates (ammonia only because I cannot find any scientific literature on fish exposure to nitrates directly). Different species of fish tolerate ammonia to different degrees, which I assume is due to the fact that their bodies metabolize (maybe improper terminology) it differently. For example, some fish show total mortality at 48hrs of 1.0mg/l as opposed to not until well over 2.5mg/l in other species of fish.

Can the same be said for nitrates? Do they process it differently? I also have always read that water conditions and diet are two top contributors to HITH and HLLE

 

[Percula9]

The pH of a tank changes the toxicity of ammonia. The higher the pH the greater its toxicity. At lower pH NH3 is converted to NH4 which is ammonium, and is less toxic to fish. This is why fish survive the trip in the bag from the Indo-Pacific. Most fish can tolerate nitrates without a problem, but not inverts. They are extremely sensitive to it. Though there is probably differences in tolerance of nitrates between different fish species. Since NH3 is so much more toxic than NO3 most fish will suffer ill effects from it at low levels. Though fish like Tilapia can take very high levels of NH3 and generally poor water quality.

 

[greenbean36191]

The Cl ion concentration in SW makes marine fish extremely tolerant of nitrate. The tolerance varies, but nearly all marine fish tolerate concentrations well above 100 ppm without harm.

 

[HoopsGuru]

I re-read my question and it appears too wordy, so I apologize that I'm not clearly asking my question. Let me try again.

Different fish, both FW and SW, appear to be affected by ammonia differently. For example, in a study on Amazonian fish, one species had total mortality in 48 hours at 1mg/l of ammonia while it took other species until well over 2.0mg/l of ammonia exposure before they died.

My question essentially is: can the same be said about FW and SW fish regarding nitrates? In other words, will some saltwater species be able to metabolize or otherwise process it better than other species. Or, are nitrates themselves toxic to fish in the same way (in other words, do all fish likely process them the same way and, in general, a certain nitrate level will be toxic to all).

Does that make any better sense? I'm not interested in whether ammonia is more toxic than nitrates, I know this already. Ammonia is only referenced because I am only finding scientific literature on ammonia....as of yet I can't find any studies on nitrate toxicity.

 

[Percula9]

Nitrates in fish only systems just not a problem, so I guess they just don't do those kinds of studies. Nitrates are a problem for inverts and cause microalgae problems. I have never seen a nitrate level high enough to cause mortality in fish.

 

[seapug]

Saltwater parameters vary relatively little everywhere in the worldand ammonia doesn't last long in it, but the same can't be said for freshwater, so you will probably find more freshwater fish that can tolerate higher levels of ammonia than saltwater fish.

I'm sure there's some freshwater bodies with naturally high ammonia levels that support fish.

 

[Percula9]

Fresh water fish can tolerate higher NH3 levels because the pH is lower. The equilibrium is shifted to NH4 which is less toxic. When you measure ammonia with a test kit, your measuring what is called the TAN( total ammonia nitrogen). You are measuring both NH3/NH4 or TAN. I have a chart based on pH and it tells you the ratio of one to another.