To all of you that are telling me not to worry, I would have agreed with you as of a few weeks ago. I do water changes about once every other month on my 120 with 2 oscars, a pleco, and 2 turtles. They are fine. I'm sure the nitrates in there are at least 60 ppm most of the time. But in my 90 my rtc is breathing heavily and starting to get gill curl. I think I will get a pothos plant and put it in my ac 110.