I seem to remember being advised to not clean the canister for at least six months after you set it up. I have a 406 on my 55 and have had a large sponge on one of the airstones for the last six weeks or so. While the 406 isn't a huge filter, it's pretty big on a 55. If you clean the canister too often, you may be disturbing the nitrifying bacteria. Ditto with tank surfaces. I have foam on the bottom tray, Matrix on the next two, and rings on top. I know the pond guy and the aquarium science guy dump on Matrix, but my water seems fine, my fish are all active, eating well, and happy.
I had a polishing layer on top of the foam and opened the filter to check it after 2 months. The polishing layer seemed to be dis-integrating but Not much funk at all. I took out the polishing layer and left the media alone.
Over the first few months I was having problems, serpae tetras dying...cyano, which I zapped with UL bg slime remover... As I put in more plants, left the filter alone, and went longer between water changes, the tank began to establish itself.
Right now I'm 2 to 3 weeks between gravel vac/water change, usually about 30 - 40%. I'll be sticking to this schedule. Ammonia runs 0, nitrite 0, nitrate 20 - 40, pH 7.2ish, temp 76F. The water's not as crystal clear as some I see on the inter-tubes, but it's pretty good.
The test to see if I've actually learned anything will be the next tank.