When I clean the cannisters in my tank, all I do is turn them off..and pull the
output hose out of the tank and put it in a bucket...this creates a siphon in
the opposite direction of the way the pump goes....backflushes it nicely. You
may be able to figure something out from this..but thats what I do.

Barry wrote:

I have a tetra canister filter. Seems like it's been about a year since I
cleaned it.
Last time I disconnected it and simply cleaned it out. I'm wondering if I
can some how reverse the
water flow to clean it out? I assume it has good bateria at the bottom, but
I'm sure there's lots of
gunk down there as well.