I would definately keep them, they are significantly more rare than the surrounding animals, and if i can remember from scott micheals coral book(i loned it to a friend so it is not at hand to reference) im fairly sure they are a corillimorphian and as such will not be roaming around your tank like an rose anenome, while it can eat fish, so can an elephant ear mushroom and certain other mushroom corals, that pseudocrynactis polyp is very pretty and quite honestly i am jealous and wish i had my own.
