The "canisters" are actually Ocean Clear filters mounted up side down. The top vent is now used for drain and the drain now on top is the vent . every thing is valved off with union ball valves on the down stream side of the valve. every thing is mounted on a separate board that can be dropped down with the valves shut. The only things I would change is use 2 heater modules, and the air lines push onto hard tubes glued into the bottom of the tank. I can't work on them without draining the tank. I haven't had to yet. The heater capacity isn't enough with 1 heater capacity When it's cold.