Connecting 3 canisters was actually an example, but I am really thinking of connect 2. Reasons are the existing one is too strong for my Discus tank, so instead of keeping it at a dark corner, I may use in to filter water :-/through another canister to achieve better filtering effect and also buffers the turbulence it generates. I'm not inclined to use a prefilter instead because I would like debris to be vacuumed into the canister. I wonder whether using a much longer rubber tube for the inlet or outlet will work in reducing the strength of the motor.