Hmmm ... Haller Round Stingray. I take it you mean - Urobatis halleri AKA the California Stingray or Round Stingray. They generally do best in water temps between 60-72F. Fairly hardy when kept at those temps. Feeds on mostly shrimp, krill, & black worms.
While some sources claim a standaed 180 gallon will keep it for life. Truthfully a tank or pond of at least 350 gallons would be better.