Designed to form a water-tight seal, the Aquascape Black Silicone Sealant for Ponds is an extremely versatile medium. Not only does it seal the Aquascape Skimmer and Biofalls filter, but it can easily be incorporated into the construction and decoration of any aquarium or terrarium! This silicone sealant is very easy to use, and non-toxic when dry, making it completely safe for fish and other pets.