If it's not a terrible infestation, just try the aiptasia X type products you can buy at LFS. Sometimes it can take a few tries to get one killed, and sometimes other babies sprout up, so just keep an eye out for them.
There's a nudibranch that eats aiptasia, some people here have tried them, but they may not be necessary in your case.

If it's majanos, the work is more tedious, but more likely to yield immediate results as well, without the little things creeping back up on you later. I used the technique described at Melev's Reef here:
http://www.melevsreef.com/pics/bta/not/majano.html