I have a canister filter that is rated at 100 gph which is more than sufficient for the 20 gallon tank I have him in. He has a reptile light providing uva and uvb along with a heat lamp... the tank setup isn't the problem. I've had this turtle for more than a year now and he was doing fine before the move. The only thing I thought of since my last post is that my new place has a water softner and I don't know how that affects the water.