Our round 2 inch high by 4.75 inch wide sponge filter complete with weighted base and tube to hold the airline will help keep ammonia down in aquariums up to 40 gallons. This is a great for small to mid-size aquariums. Used with an external air pump and connected with airline tubing, sponge filters provide the simplest means of biofiltration for an aquarium. Just keep rinsing every few weeks.
