An external filter for an aquarium includes a canister filter having a filter assembly removably oriented therein. The filter assembly includes at least two stacked trays releasably secured together in series. The stacked trays include a compartment for holding filter media. In one embodiment, the trays are releasably secured together with a strap. In one embodiment, the filter assembly also includes a handle. In one example, the strap forms a portion of the handle.