Cmor, although the facts you give are correct it should be noted that even though marine fish are susceptible to NO2
poisoning, it is uncommon due to Chloride and possibly other factors such as overall health status, previous ailments, D.O., etc. Studies have shown that marine fish can survive at over 100ppm of NO2
without incident. NO3
is also reasonably nontoxic to marine fish and elasmobranches even over 100ppm (have seen many elasmobranch aquaria way over 300ppm without incident). Most of the time, ime, elevated NH3
concentrations ("new tank syndrome" during cycling) can have acute toxicity effects by causing respiratory distress due to fusion of the gills or "ammonia burn."
Overall, I do agree with others to return the fish (depending on NH3
measurement, damage may already be irreversible) and cycle thoroughly before continuing.