Killing Asterina stars

[asylumdown]

My display tank currently has zero asterina stars. My live rock came straight from the frieght plane from fiji in to my tank (never touched a holding tank), and I've never introduced any further outside sources of rock to my tank specifically to avoid unwanted hitch-hikers. I break all frags off whatever bases they come on, and the limited LPS I have are all smooth skeleton species that I was easily able to inspect and scrape clean of anything I didn't want.

I'd like to keep my tank free of asterina stars, but I picked up an acans frag last week that's fused to a reasonable size of live rock. The tank it came out of had both asterina stars and flatworms, and now in my coral quarantine tank (it's the only thing in there) I have seen a couple of both species walking across the glass. I've got flatworm exit here to take care of the flatworms, but the rock is too porous and convoluted to trust that I could for sure remove all of the starfish, so I'm wondering if anybody knows of a dip or solution that will kill the asterinas without harming the coral? Ultimately I'd like to cut away most of the rock the acans are on, but it's too dense to cut with any of the tools I have.