To the person who said minimum 100 gallons, you know nothing about elasmobranches. As already stated there are two species of rays which fall under the "Blue Spotted Ray" category. The one which is available more frequently is very hard to keep and often dies from unknown causes. Rays of any specimen need wide tanks, atleast 30" minimum, and a decent length. Gallon wise I would say atleast 400 gallons for any of the "Blue Spotted" specimens, and nothing below 250 gallons for anything else.