check out this link first.
'http://reefcentral.com/forums/showthread.php?threadid=689929
well the tank would be big enough..... its just that if you go and fill it up with liverock and cover the sand and its burrowing area then your tank will be far too small.
it could be done imo but would need very careful planning and placement of the live rock and coral so that the majority of the tank remained rock free and left plenty of room for the ray. and i mean plenty of room..... the tank in the link is 1700g so he could fill it up much more then you could in a 300g.
so if you were to get a blue spot ray (bad rep for being hard to keep btw) max disc size is around abouts 30cm, so you need to make sure you have 90cm minamum distance front to back of clear area and then i would think 5 or 6 feet long area clear of rock also , so that would leave a sand patch of 90cm by 1.8m, (btw i dont know what the footprint is of a 300)
the rest you could fill with rock and cover with your coral, but dont forget SPS dont do well in tanks with too much nutrients in the water so as far a bio load is concerned i dont think you could have many other fish for tank mates without it effecting the sps corals.
hth and good luck if you go ahead, its certainly something different but i think it poses lots of headaches too!
adam
