12 Oz. Pond and Stone Insulating Foam Sealant

GREAT STUFF Pond and Stone is a polyurethane-based foam sealant designed for use in water features. By expanding to fill gaps and cracks, it works as a water-resistant sealant to help direct the flow of water in waterfall, pond and streambed construction to go where you want it to go, not under or behind rocks. The foam is black to blend in among the stones and shadows. It cures in 8 hours to create a water-shedding bond for stone, rock, masonry, concrete and most other building materials. It's perfect for water features from fountains to koi ponds because it's safe for fish.