Have you tried Pitho crabs? They are supposed to eat it. The ones I have graze on algae all the time, I have to supplement them with nori.Following because I’m dealing with the same. Tried all the same things. Currently on second dose of flux rx which is working but some spots seem immune. Sea hair didn’t touch it, snails don’t touch it. Beyond frustrating. If my scape wasn’t glued together I’d rip it down and h2o2 the whole thing