Two Little Fishies ATL5445W Ball Valve for Regulating Water Flow, 1/2-Inch Two Little Fishies Ball Valve Barbed Aquatic Ball Valve for regulating water flow Used for devices such as canister filters, pump return lines, protein skimmers, calcium reactors, etc. Two Little Fishies Ball Valve Barbed Aquatic Ball Valve for regulating water flow Used for devices such as canister filters, pump return lines, protein skimmers, calcium reactors, etc. Used for devices such as canister filters, pump return lines, protein skimmers, calcium reactors, etc.