I think in order to work the canister has to be lower than the level of the intake...or something like that. It does need to be lower than SOMETHING, I'm just not sure exactly what that is 
It depends on a gravity siphon for the intake, the pump is only for the output. (Correct me if I'm wrong please)
It depends on a gravity siphon for the intake, the pump is only for the output. (Correct me if I'm wrong please)