Once they are established in a permanent residence and kept under the proper conditions, freshwater stingrays are generally healthy creatures that will develop few if any major medical problems over the course of their lives. However, there are a few minor conditions that might occasionally pop up, most of which are found in newly-aquired specimens.
Fish lice (Argulus spp.)
The creature this visitor describes is most likely a fish louse, a small crustacean that often hitches a ride on fish and snacks on their blood. Small wounds created by these creatures can develop into bacterial infections, and they can interfere with the ray's breathing if they become too numerous and cluster around the gills. Many freshwater stingrays arrive at their appointed destination covered in these parasites, which luckily can be removed fairly easily with forceps and a little patience. From what I understand, there is also a newer medication called Dimilin that can be used to get rid of these crustaceans without hurting your rays. Do not use Dylox to trean an Argulus infestation, as it is toxic to rays. For more information on Argulus spp., visit the page referenced below or Ohio State University's Parasites and Parasitological Resources.
Ichthyophthirius multifilis (a.k.a. "ick" or "white spot")
Based on my own personal experience and things I have read or heard from others, freshwater stingrays are not especially prone to ick, if they are even able to contract the parasite at all. A friend of mine who has been keeping large numbers of rays since the 1960's has never once seen a case of ich, even when the teleosts he was keeping with them were heavily infected with the parasite.
If the other fish in your ray tank have ick, never ever add any copper-based anti-parasitic medications! This will make your rays extremely ill. Move the other fish to another tank and treat them separately.
Laboratório de Helmintologia Evolutiva is a site dedicated to the different parasites of the Potamotrygonids. Very highly recommended.
Usually this sort of problem is indicative of another underlying condition, such as a wound or a bacterial infection. Once the causal factor is eliminated, the fungus can be cleared up fairly easily by adding aquarium salt and raising the water temperature by a few degrees, or by using antifungal meds (see below for a list of ray-friendly products).
Fungus around the base of the tail spine are relatively common among newly-imported rays. Many exporters insert a small piece of plastic or latex tubing over the spine to protect against being stung during the shipping process. Unfortunately, this can damage the tissue surrounding the spine, which leads to infection. The tubing can easily be removed when the rays arrive at their final destination by holding the end up with forceps and carefully slicing it down the middle with an exacto knife. However, if it is left on the spine, fungus can quickly develop where the plastic meets the base of the spine. If this occurs, remove the tubing and add some aquarium salt and/or some ray-safe antifungal meds.
Occasionally, exporters will use bamboo or some other type of plant stem to cover the spine as opposed to the more commonly used tubing. This can be problematic because decaying plant matter is practially a magnet for fungus, and unfortunately, this "bamboo" is a bit more difficult to remove. If you think that you can get it off relatively easily, go for it, but keep in mind that forcing it or tearing off the spine can cause the ray a significant amount of stress and do more harm than good. If it simply will not budge, your best bet is to go ahead with the salt and antifungals and wait for the spine to fall out. Who knows -- if you're lucky, the bamboo might even soften up and fall off on its own.
© 2007 K. Birkett.