Freshwater Stingrays

Question
We are interested in purchasing a freshwater stingray.  However, we shared this with a mutual friend and they advised us not to purchase one.  They purchased one previously from a fish farm and it died.  Here's information we received.  The tank was 150 gallon tank it's newly set-up.  They had 8 African varieties that never came close to the stingray. However, two Precoe catfish seemed to feel threaten and one sucked the top side of the stingray until it bled in one spot.  I saw the stingray and know that it was very vibrant before this encounter.  Later that night the stingray went under a rock and died.  Oh, I forgot to tell you the aggressive "precoe" was removed immediately before the stingray died.  

Are other fish threaten by freshwater stingrays?  Where can we find information on fish that are compatible with a stingray?

Answer
Hello Marinette:  Stingrays and Octopi are extremely difficult to keep in captivity... those are creatures that are best left to people who have masters degrees in marine biology because their needs are so specific.  Places Monterey Bay Aquarium keep them because their tanks are huge.  The water chemistry and other parameters in a smaller tank such as a 125 gallon.... change to often for species that are so delicate.  I would not purchase either.... dave