i also have 2 fluval 4+ internal canisters im planning on keeping in there, im just looking for something to replace the rena 4 canister i have under it at the moment, it doesnt seem to do much, its 2nd hand and it has 'issues' so im planning on treating myself, or should i say my fish, to a new filter. my tank is planted, though no CO2, so im thinking fx5 would be best option? thanks for the input so far everyone.