To Control Parasites in Fish Only Marine Aquariums.Treats Skin and Gill Flukes Internal and Eye Worms.Internal worms and body flukes can be devastating to fish in a marine aquarium.Marine Anti-Fluke and Wormer contains flubendazole which is lethal to skin/gill flukes and internal/eye worms.Use when it becomes apparent that fish are becoming thinner (\"sucked in\") and are continuing to feed this indicates an internal worm is starving the fish. Skin flukes will cause fish to rub against surfaces in the aquarium to relieve the irritation caused by the parasite. Gill flukes will cause the fish to gasp at the surface and then become increasingly lethargic.Caution: This product contains flubendazole and cannot be used in reef aquariums or where marine invertebrates are present.