Im running 2 emperor 400 on a 72 gallon bow face aquarium. I have about 2 dozen guppies, about 6 tetras and 3 baby red belly piranha's. For some reason my water stays cloudy. The tank has been established for a few months now, but the water remains cloudy. Filtration is adequate(both filters are rated at 80 gallons). Even after i use some water clear it stays cloudy. PH is at 6.5, ammonia is next to nothing, nitrite is 0 and nitrate is about 40 ppm. What could the problem be?