You can breed stingrays and make a profit. I am speaking from experience here. With a solid breeding group of 1M to 3 or 4F in around a 1000 gallon setup you can make a solid profit. You do not need to feed stingrays any special food from the fish store. Go to your local Asian super market and get some frozen food or fresh seafood to feed them, they love it and it is usually a lot cheaper than the food you get at a lfs.