Its from my buddies 75G....free sand bed area is approx: 24 x 30, and the star will cover half of that easy, but spends 99% of the time under the main shelf rock. My tank is 125g. they spend almost all their time within rock structure unless hunting (usually at night). SWo really IMO not to dependent on free sand area (albeit not nice).....so I really dont have an answer....and remember that they need to be fed.....