Stingrays will eat a wide variety of foods. Maintaining a varied diet is extremely important in captive animals, as monocultural diets incur a risk of nutritional deficiencies. Stingrays are very active, and should be fed at least once a day, preferably twice or even three times daily. The daily diet can be varied in order to create some environmental enrichment as well as balanced nutrition for the rays.
First foods for newly acquired rays should be blackworms or tubifex worms. These foods seem to be the most readily accepted, and are small enough to be inadvertently ingested either by mouth or through the spiracle, thereby giving the ray an opportunity to taste these possibly unfamiliar foods by chance. Foods that have been used for very small specimens, such as the teacup rays, are small insect larvae such as mosquito larvae, small shrimp known as ghost shrimp or glass shrimp, live adult brine shrimp, and blackworms. Chitinous foods such as shrimp provide less nutritional value than do soft-bodied foods, and so should not be used as sole food items.
The best way to be certain that your new stingray is feeding is to watch the spiracles as the ray passes over food on the bottom of the tank. If it is eating, you will see the spiracles opening and closing rapidly, or fluttering, as the food is ingested and water is passed from the mouth and out the spiracles. Once you observe a newly acquired ray readily feeding on black-worms or redworms introduce finely chopped night crawlers in small quantities. Once stingrays recognize these as food, most will readily eat them. Later, experiment with other types of food.
Types of Food
Feed live foods, including blackworms or tubifex worms, in quantities adequate to allow a small amount to be left in the tank so the rays can browse later. However, when cleaning the substrate, note whether a significant amount of living worms is present; blackworms and tubifex worms will colonize the substrate if not eaten and add to the nitrogenous waste production in the aquarium.
Nonlive, Nonaquatic Foods
Chopped earthworms, redworms, or night crawlers and any nonlive, nonaquatic foods should be fed in smaller quantities to prevent any overlooked food from decomposing in the tank. Keep in mind that stingrays have relatively small mouths-a 10-inch (25-cm) ray may have a mouth that is 1/2 to 3/4 inch (13 to 19 mm) wide, so chopped food items must be small enough to be eaten easily. If a ray ingests a piece of food and repeatedly spits it out and ingests it again, this usually indicates that the particle is too large. Some ray species, such as antenna rays, have extremely small mouths relative to their size.
Once acclimated, rays often develop techniques for eating larger pieces of food; for example, newly imported rays may have difficulty consuming even small chopped pieces of night crawlers. Eventually, however, they learn to eat an entire worm by sucking it into their oral cavity without chewing. Newly acquired rays also often ignore feeder goldfish but they quickly learn to chase down and consume feeders, even learning where they hide in the tank.
Commercially Prepared Foods
Stingrays may learn to eat other unfamiliar foods such as brine shrimp, pellet foods, or other commercially prepared foods. While there is probably no harm in offering these foods to rays, it is best to use fresh, live, or frozen foods as the dietary staple. Although stingrays often do not initially accept frozen or other nonliving foods, they may soon learn to eat these foods after they have been acclimated. A benefit of frozen foods is that they are less likely than live foods to introduce diseases or parasites.
Occasionally, a well-acclimated specimen will fail to gain weight, even though you are offering enough food. Several things may cause this problem; the most likely possibility is that it is not competing efficiently for food against other fish in the aquarium, or it may have a parasitic infestation. Stingrays occasionally do not seem to learn where foods can be found during feeding times, and are always in the wrong part of the tank during those times. In these cases, it is helpful to hand-feed such specimens. By this I do not mean feeding with your hands. Although some aquarists do this with stingrays, I do not recommend it because of the possibility of being accidentally stung. Remember that stingrays are wild animals, and no matter how accustomed your specimens become to your presence, it is impossible to always accurately predict their response to humans. Instead, you should always perform the hand-feeding of specimens with long forceps or a similar instrument. Stingrays generally avoid metal objects and appear to be frightened by metal; however, because they can sense metal, they will quickly learn that when there is a metal object in the aquarium, food is being offered. In this way, you can teach your stingray to feed directly from forceps, and selectively feed it more food.
Simply hold a night crawler (or a piece of night crawler) in the forceps, and hold the worm in the aquarium so that the ray can touch it with its fin. It should eat the worm immediately. After a few feedings in this manner, allow the forceps to touch the ray while it is eating the worm. It will quickly learn to associate the forceps with feeding and soon you will find that the ray will pounce on the forceps as soon as it touches it, eagerly looking for a treat!
How Much and How Often
The key to having well-fed stingrays in your aquarium is providing plenty of food. Unlike most fish that swim quietly between feedings, stingrays search constantly for food, looking under and around tank ornaments, moving driftwood, rocks, filters, and even other fish! This high activity level translates to a high metabolic rate, which means that while searching for food rays continue to burn energy. If they use up energy looking for food, but do not find any, they will lose weight. To compensate for this loss of energy, it is essential to provide adequate food. I cannot stress this enough. Hobbyists sometimes tell me that they feed their rays three times weekly, thinking that this is adequate. Stingrays should be fed at least twice, and usually three times, daily. In spite of these frequent feedings, rays will still constantly look for food between feedings!
When feeding significant quantities of live feeder goldfish, it is wise to add vitamin B1 to the feeder supply. Goldfish contain the enzyme thiaminase, which destroys thiamin, or vitamin B1, and this vitamin must be replenished. It should be your practice to add one 50-mg tablet to each 500 gallons (1893 L) of water every two weeks. You can add the tablets directly to the sump of the wet-dry filter; or as an alternative, the tablets can be added directly to the tank.
Brendon Turner maintains The Animal Gazette - a weekly edition of helpful articles for pet owners. Visit AnimalGazette.com for information about cats, dog breeds and tropical fish.