I'd say it was a H.crispa. One of the lesser used names for these is 'leathery anemone' and if you look at the column in your pics you'll see why. The other indicators ie brown tentacles, purple tips are there so I'd say you have what you want. Are those last two pics a feeding sequence ? Did it eventually take the prawn completely ? I'd suggest smaller pieces of food initially. Sometimes large pieces will be taken but spit out within a couple of hours partly digested. But see what happens with yours and use that as a guide.