Because tap water contains chlorine and heavy metals it is toxic and aggressive to fishes’ delicate skin and gill membranes. Fresh Start rapidly removes these toxic chemicals and metals and contains a natural colloid, which coats the fish with a protective barrier. Fresh Start should be used when starting a new aquarium, or when carrying out regular water changes. The treatment should also be used whenever you top up your aquarium or if you suspect heavy metal poisoning. For use in coldwater and tropical, marine or freshwater systems. Pack will treat 500 litres of water, and includes a pipette, measuring cup and a guide to fish health.