They're sure a pest. They're, I take it, the white ones, not mini-brittle stars?
The white ones with odd arms are asterinas. There's somebody on RC selling them...maybe you could contact that person and arrange to ship a lot of them to him for the price of shipping...or a frag.
They're good in small numbers, but your tank is evidently Asterina Love Nest #1. Pretty soon they'll have eaten up their food supply and will be eating things you wish they wouldn't, because they will try to survive. Tweezers are good at picking them up.
Think of it as nutrient export, just the same as culling algae from a fuge.