Hermits don't really eat algae unless your barely feeding your tank and they can't get any other food. Red legs and scarlet consume more algae then blue legs in my tanks. Trochus snails are awesome algae eaters and live very long compared to turbos, which u haven't had much luck keeping.
They are definitely cool, I have a small spined sea urchin, about a year old, picked him up for 10 dollars and threw him into my 6 gal. He has grown about an inch, and is in my 29 now, has yet to do any noticeable damage to coral, but has put a dent into my algae. Very hardy too, there was not a lot of algae in my 6 gal and that tank crashed, this guy survived everything. I would stay away from the long spined urchins though, saw someone try to move rock and got the urchin instead lol.