Tetra AlgaeControl Water Treatments, 3.38-Fluid Ounce A precision dropper top helps you administer the proper dose to your aquarium. Tetra's state of the art formula makes it the most highly concentrated algae control product available on the aquatic market today. This item is not for sale in Catalina Island This item is not for sale in Catalina Island A precision dropper top helps you administer the proper dose to your aquarium. Tetras stateoftheart formula makes it the most highly concentrated algae control product available on the aquatic market today. This item is not for sale in Catalina Island This item is not for sale in Catalina Island