[Delphinus]

This fish seems to have half a dozen different common names. I can think of -
- <matted,mottled,seagrass,bristletail,sargassum> <filefish,leatherjacket>

.. all which refer to the species Acreichthys tomentosus.

My experience with this species (I've had two now, first one I lost to jumping).
1) I guess I'll start with that last point, they can be jumpers. I was surprised to find they could be jumpers. Although I guess not HUGELY suprised, any fish can jump but some you'd think would be more predisposed than others. Anyhow, you should have a tank covering (netting, canopy, fence, or whatever).
2) Both eventually ate aiptasia but both took their time. In fact, the one I have went now went several months before discovering a taste for aiptasia. Then all of a sudden one week they all disappeared. So yes, they do eat aiptasia, although not always is it immediate.
3) As with any fish that eats aiptasia, there is a risk they'll eat other things you may not wish them to. My first one was a fairly model citizen, but my second one has done some some damage to my Acan's and my torch coral. However other corals he's left alone altogether.