Bacto-Surge Sponge filters are an air driven sponge filter that provides excellent biological and mechanical filtration. The foam block is reusable and can be rinsed repeatedly. Sponge filters are great for quarantine and breeding tanks.
Rivers to Reef says: These are our favorite type filtration if you are trying to be economical. While they are not the most attractive, they provide excellent filtration for tanks with small fish, shrimp, or fish with long flowing fins (for example Bettas). If you are just running an airstone, why not put a small sponge filter on and put your air to work?! If you are in areas that are susceptible to power outages you can even run a battery operated air pump to these during outages to keep your fish filtered and aerated! And finally, these sponges last forever (not in the literal sense). We have sponges in our tanks that are more than a decade old!
Note: Air pump is not included with sponge filter.