I didn't even think about sealing the back of mine. It looks the same as when I made it almost a year ago. (It's not flush with the glass as I made a built in 'fuge behind my wall). I think sealing it is basically just so you can glue sand to it to make it look more natural.I love this idea. I'm setting up a new tank. Back into the hobby after 15 years away. One question, do you epoxy the back side as well to seal it up? Everyone is showing the front and I want to get the back right as well.
My turbo snails eat the foam on my wall..Im thinking about doing this to cover my corner weir, will urchins and sea stars damage the foam even when coated in epoxy resin and crushed coral?