Gorilla glue is a urethane based adhesive which is different from Super glue...but it is water resistant. I have not used this in water inside my tank yet. But, Super Glue is obviously reef safe since most of us use it regularly to adhere rockscapes and frags. If in doubt, or someone else doesn't respond with a definite confirmation that Gorilla Glue Epoxy is safe, then maybe change to Super Glue.