My oscar has suddenly become lethargic and hangs around at the bottom of the tank. I recently ridded the tank of a red devil because it was etting very aggressive and I had noticed spots on the oscars head where it looked like he had been attacked by the red devil. The spot looked like to was healing and a divit would stay where the spot used to be. They seemed to stop appearing when the red devil was taken away but I'm not sure. Now he has had several white poos and they are longer than normal. He also does not want to eat as often. He is only 5" long and I am worried his growth could become stunted from this. I keep the tank very clean with water changes occuring at least twice a week. Nitrates always under 40ppm and normally around 20. Do you guys think it is hexamita and how should I treat it?