Proper cleaning of Eheim Canister?

[pbohart]

Hey folks -

I have an Eheim 2215 that I am going to clean for the first time. Can someone help me out with instructions on the proper way to do this?

Should I clean out the sponge layers?
Should I scrub the rocks/tubes?
Do I need to keep any parts submersed?

I basically do not want to destroy the "good" bacteria that has grown to eat the Ammonia - but I do want to clean the filter.

Thanks!

Patrick