Brittle star question

[pensfan84]

Last weekend I got some live rock from someone.And have noticed that there are a lot of brittle stars in the rocks.It is hard to judge how many there are but everywhere you look you see there legs hanging out.I would guess there has to be at least 50 of them.I only have a 12 gallon nanocube going.My quesion is are they going to pose a problem in the long run with over taking the tank?And should I consider trying to ride my tank of some of them?Or just let them be and will there numbers go down on there own.