are you sure its not just a blue spotted, or a blue spotted ribbon tale ray?
if its a ribbontale they dont live that long in any aquariums, no matter what level of experties the keeper is at. they are very hard to get to feed. i fed mine blood worms and ghost shrimp...believe me i spent over 50 bucks buying diff. foods to ge her to eat. sh she died a few months latter. they get atleast 27 inches long with a disk width of 11 inches.but for the tank size ur going to need atleast a 300 gallon. i truely belive they should be left in the reef.
if its a blue spot they are a little bit easier to keep, but still hard to get too feed. blue spots get up to 40 inches long....ur going to need a tank atleast a 300 gallon. again i really think any ray should be left on the reef... unless put in a aquarium like novices...over 100 gallons. and very good water quality and takin good care of, as far as tank mates and food.