Nutrafin basix 7 Day Fish Feeder has been specifically formulated to provide food and multi-vitamins for your aquarium fish for up to 7 days. The slow release feeder provides a varied diet of pellets and multi-vitamins for community aquariums up to 10 U.S. gallons (37.8 L). For larger aquariums simply add one block per 10 U.S. gallons (37.8 L).