How to find a freshwater stingray
Wild-caught freshwater stingrays can usually be obtained by your local fish store upon request. You also can order them directly from various importers over the Internet, but keep in mind that in many cases, you are responsible for picking the fish up at the airport. In addition, there are no guarantees that your fish will be alive and healthy upon their arrival.
Several stingray species, such as the ever-popular Potamotrygon motoro, have frequently bred in captivity. If possible, it is better to purchase tank bred animals for a number of reasons. They have not endured the extreme stress of importation, and they are already used to aquarium conditions and the food they will receive in captivity. In addition, they are not likely to carry many of the diseases and parasites that often accompany wild-caught animals. Overall, they have a better survival rate, and are consequently less of a financial risk.
Choosing an adequately-nourished, healthy animal is crucial for success in keeping stingrays. Here are a few things to consider before you buy:
Appetite -- Stingrays in good condition are perpetually hungry, so lack of appetite in a fully acclimated animal is usually an indication that something is wrong. A well-nourished ray should have a somewhat rounded back and a thick tail base. Severely protruding pelvic bones (two points on either side of the tail base) or an indentation on the forehead between the eyes are both telltale signs that the ray has not been receiving adequate nutrition. The appearance of disproportionately large gills indicates that the animal was once in good health, but has lost a great deal of weight over a relatively short period of time, probably due to the stress of being shipped.
This is not to say that all thin rays will inevitably die. As long as the fish has a hearty appetite, it has a very good chance of survival, and in most cases they will put all of the weight they lost in shipping back on in no time (see photos below). If you're in doubt, ask the salesperson to give a feeding demonstration.
Open wounds or sores -- Injuries may occur in transit due to overcroweded shipping conditions, or as a result of a confrontation with a tankmate. Although these fishes generally heal very rapidly, especially severe wounds (i.e. - half the disc chewed off) can become infected with fungus if not promtly treated.
"Death curl" -- If a ray is severely stressed and under-nourished for a long period of time, it may begin to exhibit the so-called "death curl", in which the edges of the disc curl upward instead of lying flat or slightly gripping the substrate. This most likely occurs as a result of damage to the nervous system and the deterioration of muscle tissue in the disc, and most rays who exhibit it are apt to die. There are varying degrees of this condition, from slight to extremely severe, and sometimes normal disc movement can be mistaken for it, so just watch the animal for a little while and try to get a feel for its overall condition.
Female vs. male
Deciding whether to get a female or a male ray isn't a particularly crucial decision. Female stingrays tend to grow quite a bit larger than males in most species. Many hobbyists have also observed more aggressive behavior in the males. But other than that, your ray's gender really won't make much of a difference.
Sexing rays is a simple matter. Males have tube-like sexual appendages called claspers growing out of the inside of their pelvic fins, while females have unadorned "feet". Sometimes it may be more difficult to see the claspers when you're dealing with young animals, but if you look closely enough you should be able to locate the tiny nubs.
Before you buy, it is a good idea to make sure that freshwater stingrays are actually legal in your area. The keeping of these animals is prohibited in some areas of the United States both to ensure public safety and to protect the integrity of native ecosystems by preventing accidental introduction. Here is a list of US states where they are illegal.