The camel back shrimp, the dancing, or pepermint shrimp.
Delbeek descibes this shrimp as a voracious coral eater.
I have kept several over the years and have never noted them eating caluerpa. They do however have a particular liking for LPS, especially open brains. I had to tear down a tank to remove a pair.
They do provide a lot of larvae for the system to feed on if kept in pairs, mine would spawn every couple of days.
As long as you don't mind the idea of having to remove one in the case it decides to feed on one coral you might try it. Some will spread their picking out enough that they don't do any real harm. In fact small amounts of picking can actually be desirable as this is natural and can increase growth rates in certain coral and even elicit spawning behavior. Food and light energy become critical in these situations as the coral must be able to renew itself at a rate greater than it is being eaten.
For the novice this shrimp is likely best left at the store, or carefully watched.