Easy Life Alg Exit combats green algae in freshwater aquariums, such as beard algae, brush algae and string or thread algae. It is harmless for fish, crustaceans and plants. Add 10 ml per 100 litres once a week for four week. This period may be extended if algae still remains or if spores continue to germinate. For algae prevention add 5 ml per 100 litres once every two weels. Alg Exit can be removed from the water with carbon. 250 ml.