Just remember when dealing with stingrays your not so much looking at the gallonage of your tank but the foot print. You can have a shallow tank (12") but you would need something longer and wider. The actual foot print would all depend on the species your are planning on keeping. Some can get to be larger then a garbage can lid.
yea here in the near future i am upgrading to a 250+ tank thats why i was wondering. i have fish right now that would undoubtably love a 250+ gal tank so i would want something that would need something that big