Currently I have a ray in my 150 predator reef. He is a small unidentified ray from with a 4.5 inch disk and 6 inches long, he also doesn't seem to show any signs of growth so I got pretty lucky.
Rays are the best pet saltwater has to offer. Mine begs for food, does flips, and asks for belly and head rubs. Not to mention their high intelligence. It is no wonder they are in touch tanks, they really like to have human interaction. Even more so in the home aquarium, mine has almost a internal self timer that knows exactly what times I will come and visit him. They also(at least mine) is very active and cruises around most of the day and sleeps in the sand at night.
As far as care they are good as long as you have nitrates under 10 and feed them 2 or 3 times a week.