what filters have you used and had the best results with...i have two western painted's in a 55gal and im running and emperor400 on one side and a penguin sumthing (made for 50ga tanks) and i still change water every week...i think its cause im not using filters that reach to the gravel their intake slots are at mid tank level when most the turtles waste and debri is at the bottom...so what would be a good filtration system to use ona 55gal to help keep the mess on the bottom under control. thanks all.