ok, Friday I took the rest of the infested rock out of a different system, also had bubble algae, aptasia, sponges, feather dusters, asterina stars, mini brittle stars and stomatella snails on/in it. I put the rock in a five gallon bucket of fresh water then poured in a couple cups or more of bleach. I rinsed the rock this afternoon and put it in a bucket to dry. Out of curiosity I went and hacked open the vermetids and they appear to be dead, one moved a little but I think it was just snapping back after being stretched. I believe the contact time on the first batch of rock I did was not long enough.
I would think 24hrs in a strong bleach bath, a good rinse then a bottle of chlorine remover would be a good start. May also want to take the time to thoroughly dry the rock and make sure there is no chlorine odor before putting rock into system