If you ask 500 reef keeper I'll bet the vast majority would say nitrite by its chemical nature is toxic. At what levels for different animals I dont know. I'll keep following the majority and consider it a compound to avoid. I realize this makes me a poria on this forum but that's OK.
...but would any of the 500 reef-keepers have documentation of issues that are known to be directly related to or made worse by nitrite toxicity specifically? The general belief of hazard may be due to carry-over from freshwater tanks where the toxicity is certainly more documented/researched. It also may just be from the idea that it is not measured in natural seawater much at all, so it should not be in aquariums. This is a good baseline, but not a final answer to the discussion.
Also, there may be false beliefs that are generated by other causes. I do not know this to be the case with nitrite, but it is possible that something else causes an issue but it is blamed on a different cause. This happens all the time when people assume that the last fix applied to an issue is what fixed the issue when sometimes the issue goes away due to a different reason and is noticed as resolved during the last fix.
For nitrite toxicity, it would seem to me that it is not clearly defined how toxic it is in marine environments but is not a serious primary focus when there are other likely issues, especially for new and uneducated reefers who are beginning their education.
Everyone go look at your tanks and just enjoy them. Forget chemistry for a minute and enjoy.
I agree that we should look at and enjoy our tanks. I also agree not to fix what is not broken.
...but I do not agree that we should forget chemistry or other learning necessary when our system does not go the way we want it to. (I do not think this is what you mean, but this thread is specifically about answering the questions of chemistry, so it is not the place to forget chemistry). How many reefs have ever been set up with a basic maintenance schedule of cleaning the glass and feeding the fish/corals and went on to never have major issues? Each step of complexity requires 1 of 3 solutions I can think of right now:
1. Research the issue, formulate an informed opinion, apply the opinion, measure results, keep/change opinion accordingly (when pursued long enough, this usually fixes the issue and maintains a successful tank)
2. Pay someone else to fix the issue (sometimes this fixes the issue, but you have to do research on the reliability of who you hire to fix the issue; this method does not benefit personal education as much unless questions are asked and answered with education in mind)
3. Give up, quit the hobby, get rid of reef (this obviously is the least-educating method, but is guaranteed to eliminate reef-related issues [other than, maybe, debt from setup cost])
I personally choose the first option due to my desire to learn and understand the issue myself, but the other 2 are valid options that some people choose.
Those who follow the first option will have the most useful information to pass on to new hobbyists, especially by keeping record of scientific studies and long-term experiences of those who have been in the hobby and been successful for years. Information shared by me needs to be verifiable and able to assess and answer to counter-arguments and should never be just passing on things I've heard but cannot justify.
Thanks for the discussion. Hopefully we can all continue to learn more about these issues while also maintaining successful best practices as determined by our current information.