well if it is what I think it is, kill it, but I'm not entirely sure that it is what I think it is. If it is what I think it is, I had them they had very long tenticles, a handful of inches long and when I would touch on they would retract, rather quickly really, they were attack my corals and ****ing them off. I would kill them by either taking them outside and chucking them down the street, or crushing the shell with some acrylic tubing that I had, I was more fond of the chucking them down the street method though. Although to this day I fear calls from PETA. But like I said I'm not entirely sure thats the same thing as what I had.