I am setting up a goldfish tank in a "coffee table" aquarium. The base of this tank is about 6" above the floor level. If I set up a canister filter at floor level (about 6" lower than the base of the aquarium), is that sufficient for the the filter to work effectively?
as long as its bellow the bottom of the tank you should be fine. Actually, shorter hoses should let the filter move more water and filter more effectivly.
The filter should be lower than the bottom of the tank if not water can go into the pump and fry your fish.
I have two Fluval Canister filters and they’re great! This is from their site. . .
Since the unit is a gravity fed sealed unit, the filter must be positioned below the aquarium for it work efficiently. If it is even with the aquarium or above, it will not work as expected.
The top of the motor unit should be below the bottom of the aquarium. In most cases the stand is often a cabinet and the filter is placed under the aquarium in the cabinet. A long drop is not necessary, but the filter should always be placed under the aquarium bottom.