Aqueon Silicone Aquarium Sealant creates a clear waterproof seal to stop and prevent leaks. It employs the same strength silicone used to manufacture new aquariums, to deliver an easy-to-apply, long-lasting bond. Silicone Aquarium Sealant remains permanently flexible and will not crack or shrink over time. Non-toxic and safe for use on freshwater and saltwater aquariums.