How to DESTROY bristleworms ??

[FWC]

There isn't any visible population

I used marco rock for my tank ,and I try and dip any frag I let into the tank. I find fresh water will kill a bristle within 30 seconds.

However a few have managed to get in with the frags that I didn't dip, so I want to keep something in the tank for the odd worm that manages to escape my preventative measures.