Filtration is a very important aspect of keeping turtles. Turtles can be quite messy and do eat a lot so a good biological filter is required. We sell quality internal filters which are suitable for smaller tanks and all sizes of canister filters which are recommend for larger turtle tanks. Filters that only have a sponge inside them are not recommend for turtles. Where possible Purigen and or Bio Chem Zorb is recommend to be used in all turtle filters. When upgrading an existing filter be sure to leave your old one running for at least 4 weeks before removing it. Filters need to be on 24 hours a day except when cleaning. Remember to only used discarded tank water when cleaning your turtle filter as using tap water can kill your beneficial bacteria.