I recently moved my Red Bellied Pacu from a 65 gallon tank to a 90 gallon. The move was pretty rough on him, he went completely limp once out of the tank and into a bucket of water and I thought he was dead, but then he went crazy once he was in the new tank. My 3 year old pleco found the move very easy though, not much bothers him. I put all of the water from the 67 gallon tank into the new one, and topped it off with new water. About 24 hours of being in the new tank, my sister found my Pacu upside down. We thought he was dying, but then he flipped himself over and was fine. Both fish were doing quite well and were eating regularly, but today I came back from school and both fish were dead. There was a white philm on the water surface and the tank smelled horrible (although that could be the dead fish). I checked the pH level and it was just below 7.0 and the water temp. was fine. Does anyone know why my fish died and now I can prevent further death in my future fish?