My last stingray came from a private breeder who had a couple full grown motoros and one that I believe was a reticulatus. All a couple feet wide. He had a human sized pool in his basement that was probably 12' in diameter and the sides had been altered to be 2' high. He lined the sides with thick black rubber cuz he said the rays would bite at the sides while mating and caused some damage in the past. He used two 50gallon plastic drums as a filtration device - it was a crazy thing to see but really cool to see real FULL grown (at lest in captivity) stingrays rather than 10" stingrays in a 6 foot tank that will never reach their full size.
The stingray I bought from him was the last I ever bought (when it got too big for me to house properly I sent it off to a breeding program which I hear, after he (it was a male) got over the initial scare of seeing a few females and wondering what the heck they were, did very well) but ever since, I decided if I get a house with ample room, I too will have a human sized pool in the basement and have another ray