Ok I want to make sure that I am doing the right thing. My 36g has been up and running and cycled for quite some time. This filter takes the type of sponges that already have carbon in them. I was under the impression that it is better for the tank if the filter is changed every month. The filter sponge does get very gunky I also have a biowheel with this system that I was told holds the biological media needed to keep the aquarium water in check. I usually seed the new filter with the old one in place for about a week and then I chuck the old one. Am I doing the wrong thing? I have read that some members just rinse the existing filters in old tank water after a water change but then I have read that the carbon in the filter keeps the water clean so I am confused. By changing out the filter am I losing the biological media or am I doing the right thing because the media is actually in the biowheel. My water parameters have been fine have had no problems just needed some feedback on what others do with this type of filter system.