How old is the tank? What are your water params? Size o the tank? What filter? Params of your tap water? Do you use a conditioner such as Seachem Prime when you do water changes? Temp of the tank???
All of these things could be a culprit.
Lots of advice will come rolling in once these questions get answered.
Mike
Ok, I'm baffled. Hopefully some one reads through and has an idea.
Mike
Yeah. You should have 0 ammonia. I'm thinking you have a nitrate bed somewhere, maybe in your fx5 or your substrate bed. Do a thorough gravel vac and a 50-60% water change for the next 3 days. Also I suggest you get into your fx5 and give it a thorough rinse out. Lastly, I'd try to get away from the nitrate remover. I think it's masking a bigger problem.
Mike