Fight stress - First Defense for saltwater aquaria was developed to help fish adapt to new environments by assisting the fishes' natural immune systems. First Defense promotes healing, repairs wounds and supports the immune system with vitamins and immunostimulants. Changing the environment of fish causes stress that robs fish of essential nutrients and can weaken their immune systems. First Defense is scientifically designed to provide stress relief and support the immune system, helping fish cope with stress due to bagging and shipping from the store to your tank, water changes, new fish additions, disease treatments, and other environmental changes. Fish are subject to many stressful events before becoming comfortable in your aquarium. For instance, they were shipped in bags to the store and then chased around the tank, netted and bagged before you took them home. Many times fish are not fed much before shipping so that their waste does not pollute the shipping bag but this can further weaken their immune system. As with people, a weakened immune system means a greater chance of the fish become sick with Ich or a bacterial infection. The mixture of immunostimulants and vitamins in First Defense have been demonstrated to help support the immune system of fish so they can fight off diseases. First Defense also contains buffers to help maintain the water pH. Further, First Defense detoxifies heavy metals and removes chlorine and chloramines. For Saltwater aquaria 2 ounces treats 120 gallons.