ditto on throwing the whole starfish in the harlequin tank ... i just get the starfish medium sized to minimize the mess.
i tried cutting up a sand-sifting star once ... a bit gruesome ... the exterior is a lot harder than i expected ... scissors are worthless, dulled the edge off my best knife, snapped two hacksaw blades, couldn’t find the machete ... finally finished the job with the trusty light saber! ;)
kidding aside, removing the arms just increases the likelihood of the poor starfish just wasting away IMO.