Many commercial water filters for aquariums can be expensive and require electricity to keep them running, but homemade aquarium filters can be powered by air displacement, requiring no electricity or pumps. Aquarium filters remove fish waste and food residue that can cloud the aquarium water and possibly sicken or kill fish. If needed, greater flow can be achieved by attaching an air pump to the filter, but that is not required with this filter.
This filter will work in saltwater or freshwater aquariums, and without the air pump, the filter is suitable for aquariums up to 40 gallons.
Cut the pop bottle in half, and discard the bottom half. Cut "V" shapes along the cut edge of the top half.
Place the pop bottle into the ice cream container, with the cut end down. Lead the air line from under the cut edge of the pop bottle to the outside of the ice cream container. Attach the air stone to the end of the air line inside the pop bottle.
Surround the pop bottle with gravel to keep it and the air line secure. Fill the ice cream container nearly to the top with gravel.
Place the container in the aquarium, keeping the free end of the air line outside of the water. The filter is powered by air displacement, and as air bubbles rise out of the air line, the aquarium's water will be sucked through the gravel, which acts as the filter.
To clean the filter, disassemble it and clean the individual pieces before reassembling it. You will need to clean the filter when the water first becomes cloudy or when the water flow has dropped significantly.
Ensure the free end of the air line does not become submerged in water. An air pump can be attached to the free end of the air line if you want greater air flow through your filter. Water throughout the aquarium will be sucked through the gravel and filtered. You can add other filtering materials to the gravel, like carbon, sponge or cotton, but that is not required.