how to get rid of aptasia(?)

[lastlight]

I bought two of these (maybe not the right ones?) but they disappeared under my rockwork never to be seen again with the lights on. I did spot at least one under the rocks one night with a flashlight but after that nothing.

Currently back to the epoxy technique with varying degrees of success. Tempted to try a matted filefish but I'm too scared they'll eat my corals.