Bryopsis is always a nice choice. I can send you some without much of a problem.
In all seriousness, I like Halimeda although it does soak up calcium. I think it looks nice. Some caluperas will go sexual and create problems so be sure to research if you go that route.
Do any of your residents eat algae? Any red varieties I've tried always get eaten within the week and all I have to eat it are snails, emerald crabs, maroon clown and a bicolor blenny.