Aqueon Submersible Internal Power Filters offer unique versatility, they are fully submersible and for use in both aquariums and aquatic terrariums. These filters effectively clean water using a three-stage internal filtration process: Stage 1 uses a dense foam to remove particles and debris; Stage 2 utilizes activated carbon removing toxins, odors and discoloration from water; Stage 3 uses a patented Biogrid to remove ammonia and nitrites from water. These filters have a unique design feature - directional positioning return pipe with flow control. It allows for easy vertical or horizontal positioning within the aquarium or terrarium. They are self-priming; simply position in your aquarium or terrarium and plug in. Aqueon Submersible Internal Power Filter are preloaded with an Aqueon replaceable cartridge(s). Available in 2 sizes, AT10 and AT40.