Beckett Waterfall Foam Sealant - BlackBecketts Waterfall Foam Sealant forces your waterfall to bend to your will! This easy to use black foam seals up gaps under waterfall stones, forcing water to flow over the top like you always intended. Use for filling, bonding and sealing waterfall stones Easy to use dispenser tube Completely fish safe The foam comes out black, which makes for easy hiding under and around rocks. Always read all safety, storage and usage instructions before using.