When I first started in SW I added a couple Mollys to watch my Lionfish feast. After a week or so they began popping out little babies regularly. When it was clear the Lionfish wasn't interested, I removed them and gave them their own tank. So I think they do pretty well in SW.

I don't recommend using ANY livestock for acclimating. There's no need and it isn't pet friendly. But it does make for an interesting addition to the tank.