I never just use chlorine remover, I always use chloramine remover. you never know when the water company will add some. I losts some big frontosas once because of this. aerating and regular chlorine removers will not remove chloramine. also check the whole tank for any fish that may have died and are hidden, that can make your PH crash if you have poor buffer, I found a dead fish once hidden in one of those castles you buy at LFS's