An internal filter provides an easy way to keep your aquarium clean and your fish healthy. Many internal filters cost about £6 to £13, and they can do an excellent job at filtering the aquarium water and removing contaminants. If you buy a filter that is properly sized for your aquarium, you should have no problem keeping your tank clean.
Open the filter and insert a filter cartridge. Use only the filter cartridges designed for that filter. Each internal filter uses a specific type of filter cartridge, and that filter cartridge is designed to fit the filter properly.
Attach a piece of air tubing to the connection on the internal filter. Run the other end of the tubing to the air pump on the outside of your aquarium. The tubing should be long enough so it can reach the pump without kinking or stretching.
Push the filter cartridge down into the aquarium. If the filter cartridge uses suction cups, attach those suction cups to the aquarium glass. If the filter uses a plastic base, bury that base a few inches into the gravel so it stays securely in place.
Plug the aquarium pump in to start the filter action. Change the filter cartridge once a month to ensure that the water is filtered properly.