Nutrafin Cycle Biological Aquarium Supplement features a high-concentration formula that immediately establishes a safe biological aquarium environment. Cycle goes to work fast, releasing massive amounts of beneficial bacteria that eliminate toxic ammonia and nitrites and creating a biologically well-balanced aquarium for healthy fish to thrive. Cycle is an all-natural product that will not harm plants, animals or humans. It does not require refrigeration. For fresh and saltwater use. Size : 250 mL (8.4 fl oz)