I have found it very difficult to find fish that only eat certain alga. If you use snails and hermits to keep the nuisance algae in check, you can have these kinds of algae in a community tank.
I do not have an issue with nuisance alga in this tank. The macros grow quickly so if one gets a bit of hair algae on it, I just clip it off. I am actually trying to get Asparagopsis taxiformis to grow, but it has been a struggle. I have found that by encouraging the stronger, faster growing species, the nuisance alga struggle.
But, a 180 without a tang? or angel? I have a few tangs and I have found very few alga they won't eat. I have found as long as there is something they like better to graze on (nori on a magfloat), they will leave some algae alone (Caulerpa species, Chaetomorpha species), but they would rather eat either before they eat the hair algae. To keep their tank free of hair algae, I have to let them eat everything else...
If you decide to not add herbivorous fish, and just use snails ( a lot of them), you can add small lionfish species! I have an anntenata in my reef and he does not touch any algae. That would look cool to have some algae, grasses in with a small herd of antenatas! He does eat peppermint shrimp, though....Aiptasia must be manually removed ( I let them climb onto a piece of rubble).
There are some algae genera that herbivores won't eat. The genus Halimeda has some gorgeous specimens. It does suck up calcium so you have to add calcium and bicarb when it starts to grow. But, I think seagrasses will be eaten by most herbivores.
Here is a species I just found. It was living in an algae haters tank, so it is just geginning to get new shoots. It is in my reef, with my scopus tang, a lawn mower blenny and a rabbit fish!
