Toxicity Of Nitrogen

[4seasons]

O.K. first off as a relatively new comer to fish and fish keeping I am very grateful to all the help advice and information on this site. But as I become a little more experienced I have found some information lacking. The beginners section is good, found lots of info about cycling some common problems and uncovered a ton of fish store lies. But as I progress I find myself looking for an intermediate info section. I have found some really advanced information that really goes way over my head and some really "dumbed down" info about how to cycle your tank and turn ammonia into nitrite and then nitrate. I have even stumbled across some chart about just how much ammonia your fish can tolerate at a given temperature and PH (although I can't seem to find it again and it was in percentage rather than the ppm that our kits test for). I even read somewhere that PH effects the amount of nitrite your fish can handle but not in the same way as it affects the amount of ammonia they can take. Now that I have partially completed both a fish-in cycle and a fish-less cycle I am curious just what level of nitrogen fish can be exposed to and live as well as not be harmed.

So my question is
1. Is there a chart out there that shows how much ammonia/nitrite/nitrate fish can handle at a temperature and PH without long term effects?
2. I read somewhere that high PH has the opposite effect on toxicity of Ammonia vs Nitrite. Is this true? And if so which one is better with a high PH and which one is safer with a low PH?
3. I have a basic understanding of hard water vs soft as well as the buffering affect that hard water has on PH but does hardness have any effect on the nitrogen cycle or how toxic different types are to fish or is the PH and temp the only thing that effect toxicity?

 

[Aqua Tom]

Some very interesting questions you have raised there. Although I do have some opinions, they are just that, opinions & not fact.

I am going to leave this one to our Scientific types rather than a hobbiest such as myself.


Tom

 

[CezzaXV]

1. No amount of ammonia or nitrite is good for fish, and in a cycled tank we aim to keep it at zero. Most of us have inadvertently exposed our fish to ammonia at some point or another and most of them lived to tell the tale, but it's not something you'd choose to do. As someone once put it, I'm sure there's a safe level of cyanide for humans but I'm not going to take my chances!

2. I know that ammonia at a lower pH turns into a less toxic form. Most of say it's ammonium, the more sciency peeps around here will tell you something about ions. I don't know about the nitrite, but at the end of the day the pH will not make ammonia or nitrite non-toxic to fish, though they might make it less so.

3. As you'll already know, soft water will be less resistant to changes in pH than hard water. You'll probably know that the bcteria we culture in a cycle reproduce best at a pH of 8 and the cycle can stall if if the pH drops too low. Since the processes the bacteria do cause the water to become more acidic, it can make a difference if you've got soft water. My water is very soft and in the latter stages I found I had to dose bicarbonate of soda every day to keep my pH up and my cycle moving.

I wouldn't have thought that hardness (or lack thereof) would affect the toxicity directly, but since soft water tends to be acidic (low pH) and hard water alkaline (high pH), it may affect it indirectly.

 

[grimbeny]

From the readings I have done on this, the questions you have asked could probably be answered for a few species of commercial interest, however across species the patterns are clear, any detectable amount of ammonia and nitrites will negatively affect fish health. In the aquarium hobby those questions are unimportant because your goal is simple to keep ammonia and nitrite concentrations below levels of detection.

 

[OldMan47]

Simple statement here from me. At high values of pH, even 0.25 ppm is not acceptable for ammonia. At low pH values, as much as 0.25 ppm of nitrites is not well tolerated. Although each poison can be tolerated somewhat under the right conditions, it is generally not worth it to try to get that close to toxic conditions in your tank. Keep both ammonia and nitrites below 0.25 ppm and your fish will thrive. Sorry 4seasons but I am not going to go there by recommending any larger value for either poison.

Hard water has no buffering effect on pH, it simply refers to water that has large amounts of calcium or magnesium. On the other hand high KH water does resist changes to pH. It is not normally called hard water but it has a high carbonate hardness value. Unfortunately these unrelated chemical conditions each contain the word hardness in their names. They are entirely different chemically.