Internal power filters are submersed inside your tank to pull water into the filter, pass it over a cartridge which traps the large particulates of excess food and fish feces. One or two cartridges also provide a surface area for biological activity which cleans the water of biological contaminates such as Ammonia.
Most power filters use replaceable mechanical and biological cartridge materials.
Place near surface for increased agitation, efficient oxygen replacement and carbon dioxide release. Great for lying flat in low-water habitats such as turtle and reptile water environments. Submerse in the bottom of reservoir for fountains. They can be used as the primary filtration or added as a secondary filter to expand the fish-keeping capacity of your tank. Power filters usually hang on the outside of the tank.