King British Algae Control is a natural, easy-to-use water treatment to control algae growth in coldwater, tropical and marine aquariums. Algae growth is not only unsightly, but it can be lethal to fish as it drastically lowers oxygen levels in the water. King British Algae Control contains friendly micro-organisms, which are cultivated on barley straw. It controls filamentous algae, including blanket weed, and green water in your fish tank. Captive fish live in a completely closed environment and are entirely dependent on their surrounding water. This means they are reliant on us to maintain their water quality at a suitable level for them to be able to live healthy, happy lives. When to use King British Algae Control: • If green filaments of algae are visible in the aquarium • If a green haze is visible on aquatic plants, ornaments or the aquarium glass • Once every 14 days to control algal growth Suitable for use in coldwater, tropical and marine aquariums.