I spoke to a very helpful gentleman at West Systems regarding the use of their 105 epoxy resin for "aquarium use". He stated that all though this is not the resin's intended use it has been used for aquarium fixtures for years. He stated that in 25 years he has had one complaint of dead marine life and that came down to an inproper mix of the resin and the hardner, leaving an uncured product. I will be sealing my fake background with West Systems 105 epoxy resin and 207 clear hardener with 100% confidence!!!