Unfortunately yes. My clown loaches in my paludarium managed to chew their way through the Drylok in a couple of spots and started chewing away at the foam underneath. I've heard that they've been known to do the same to concrete coated backgrounds. I imagine that large plecos would also be able to chew their way through. You could probably avoid this by throwing a coat of epoxy over the background but I'm not planning to do that (it would be expensive and I think it would ruin the texture).One question have you had any problems with plecos, catfish or any fish eating on the foam?