API AlgaeFix controls the main and most persistent types of algae in freshwater aquariums, and does so without causing harm to your fish or plants. You can use AlgaeFix as part of your aquarium maintenance routine, or to directly treat and control algae. Weekly doses of AlgaeFix will control algal growth and reduce aquarium maintenance over time. Do not use with freshwater crustaceans, including shrimp, crabs, and lobsters.