Replacement sponge for the innovative Ocean Free Hydra 20 Filter. It's smart to replace the sponge at least once per year, or when it the sponge get's to clogged.

The Cata-Pure Cartridge can last 9 -12 months depending on the amount of fish and is functional in both freshwater and marine environments. Fits all model Hydra Internal Filters, Hydra Filtron & Inline Stream units which take the square cartridge.