[Jeremy0322]

When you use a canister you are just taking all of the gunk out of the water and collecting it somewhere. Then you keep taking your water and running it through the stuff that you cleaned out of the water which will continue to happen until you clean it out. Then you clean it out, collect crap, and run some more good water through poop. You never really need to clean out live rock, but a canister filter needs cleaned out about once a week. It is just a good recipe for some nitrite build(or nitrate, i have them confused right now). Same general idea as why bio balls are pretty bad. Canister filters go have their place though, you can use them for siphoning out stuff from a sand bed, or for running carbon from time to time to make your water nice and sparkley.