Salifert Flatworm Exit works on reef aquariums that have flatworm issues. Flatworms can consume corals and are usually found when new corals are introduced to the tank. When using Flatworm Exit it is necessary to follow the directions, as flatworms can produce a toxin in your aquarium after the treatment. Multiple treatments may be necessary as well. Salifert Flatworm Exit treats up to 300 gallons (1200 L) of water.