Aquascape® 21053 1 pt Black Pond and Waterfall Foam Sealant. Aquascape Pond and Waterfall Foam Sealant makes it easy to fill joints and gaps between rocks and boulders, maximizing water flow in streams and waterfalls. There is no need for a foam gun with the easy-to-use spray can. The black polyurethane foam blends easily into rocks and gravel for a natural appearance. Ease of application makes it the perfect choice for the beginner or do-it-yourselfer. For the experienced installer, Aquascape Pond and Foam Sealant is convenient and economical for a quick touch-up on any project.