I have a 600mm x 450mm tank, 1/3 of water. When I was using a small Aqua One hang on filter with fine sponge, the water was nearly chrystal clear. (had to clean the sponge every 4 - 5 days as it got clogged up).
Now I have changed to an Aqua One CF1000 and after a 25% water change every week, and in 5 days time the fine wool is quite dirty and now the water is always light brown (looks like pee, when viewed in a white container).
There is no wood in the tank only stone. The size of the 2 turtles are approx.125mm in diam. Any idseas anyone????