Its a good idea because they dont move arround the same way as bubble tips do and no they will not in most cases cause any type of headache, they reproduce slowly and there is no issue to get several or just the one doesnt matter either way. When you get them ask to drop a small peice of rubble on top of it and turn it upside down, the rubble should stick to it or when the worker pick it up for you ask him/her to touch it and release their grip, it should get stuck to their fingers/hand if not dont get it.
No problem though its really difficult to get them to stay on gravel, i tried it for a long time, just didnt work out for me and i eventually just placed them at the bottom of the reef structure in a low flow area and they pretty much attached themselfs there and barely moved again after that, sadly i dont have them anymore but yeah thats my experience with them.
They are pretty solid and don't typically move around like other nems.
