I've zapped them before with using a needle and lemon juice, I'll have to try the reef epoxy though, that's a good idea.

You'll probably be more successful with Berghia

since you`re cooking them, consider dipping each rock (rotating sched to keep the bacteria alive) in Hydrogen peroxide?
I've used it with good success on hair and bubble algae.
Even in the tank on DENSE mats of hair algae, with the pumps off the peroxide actually pooled in the mat of algae and did it's thing and killed it. ****ed off the corals some but they recovered.
Don't ask me for the specific dosing cause I'm one of those toss some in randomly types but it DOES work.