Short answer is Absolutly not. I don't know of any fish in the world that can't tolerate nitrate levels .50ppm. Most of the community you will come to find is of the opinion that your nitrates need to be as close to zero as possible. I find that even the most sensitive of coral and fish can tolerate levels of nitrate .25-.50 with absolutely zero issue. The key is swings. You don't want a swing of any kind. If you don't want your .50ppm nitrates to go from that to zero over night. Or any of your other parameters for that matter. Keep your tank consistent and make changes very slowly. Your fish will be fine. Doesn't matter how big your tank is or what kind of fish it is or how you cycled your tank. If your tank has been cycled and you do weekly or biweekly water changes you will be just fine. Good luck. 9
In my experience the people that are alway having issues are the ones always chasing parameters. Nitrate does not become toxic to fish until it reaches very high levels. I would argue that you could keep your fish at 100ppm nitrate and it would be fine.
