Good water quality is the key to a healthy, beautiful aquarium. Tap water contains chemicals, such as chlorine and chloramines, which make water safe for drinking, are highly toxic to fish. High levels of these chemicals destroy fish gill tissue, preventing the uptake of oxygen which can lead to fish death. Even low levels irritate delicate fish tissue. Tap water must be treated before adding fish to make sure fish remain healthy. API TAP WATER CONDITIONER Aquarium Water Conditioner instantly removes chlorine and neutralizes chloramines. It also detoxifies heavy metals in tap water. The formula of API TAP WATER CONDITIONER incredibly concentrated. You only need up to 1 ml to treat 10 gallons of water. It's safe for all aquatic life and can be used in both fresh and salt water. Use during aquarium set up, water changes and adding fish.