The epoxy is aquarium safe. I make 3d backgrounds for my cichlid tanks and if I paint the cement, I cover it with epoxy. Many "professional" backgrounds are done this way as well. You just have to make sure that all the paint is covered completely. You probably will want to try to find an example of an exact one. Google 3d aquarium backgrounds or something similar. Some guys use it over the cement. You should see the brand.