I am still concerned. Ammonia is zero (I bought new liquid tests , as the old ones where giving error results), nitrates and nitrites are zero too. I raised a little bit the pH, now it's 7,5. I will try to raise the GH, but I'm still concerned about the possibility of bacterial infections. I am paying attention to his behaviour, and I think he is a little bit lethargic, he sits in the same spot for hours (he is eating ok by the way). Any idea?