According to "Aquarium Sharks and Rays" by Scott W. Michael which is pretty much the bible for keeping sharks and rays the Cortez Stingray can be kept in a 180 gallon aquarium as an adult. The species is very well suited to aquarium life and is even a candidate for captive breeding. It would probably do fine in a 90 gallon for 6 months to a year. They grow 1-2" per year and live to be about 8 years old in captivity. $50 is a very good price for one.
Are these equally sensitive to copper? I have a tank that i have topped off with tap water before (maintance account), and I would hate to see it die right away. I have never dosed any copper but the water I am sure comes through a copper pipe. Anyone have input on this? I would love to get one for the 500 gallon