I have used them with success. I put 3 in a 55g tank I had a few years ago. With time, the Bergia eliminated most of a large aiptasia problem.

I ensured nothing that would predate on the Bergia's was present in the tank. I still have the rock, now in several other tanks and occasionally see a Bergia on the glass.

They did not eliminate all the aiptasia but were part of an affective solution.