Nutrafin Basix 3-Day Fish Feeder is specifically formulated to provide aquarium fish with nutritious food and multi-vitamins for up to 3 days. The slow-release blocks contain a rich diet complete with multi-vitamins for community aquariums up to 37.8 liters (10 U.S. gal.). For larger aquariums, simply add one block per 37.8 liters (10 U.S. gal.).