The water in turtle tank is thick?

I have a Southern Painted Turlte, and the water in its tank looks thick on top within a week. Changed water, and it is the same after just 2 days. I have a filter in it and turtle looks healthy. Any idea why this happens and how to prevent it?The water in turtle tank is thick?The tank could be too small (should be at least a 40 gallon breeder) or the filter could be too weak (should be rated for triple the water amount it is filtering) or it could be both. Upgrading to a better tank and filter and feeding in a separate container with some water taken from the tank should help cut down on waste accumulation.The water in turtle tank is thick?then maybe you need a stronger filter than the one you have, turtles can be messy and sometimes require a stronger filter than recommended by the tank size :D