Captive Care Notes: Mooneye and Goldeye (Family Hiodontidae)
Although Mooneye and Goldeye pose no great difficulties as aquarium fishes, few people keep them, perhaps because they are difficult to collect in the deeper river waters they prefer. Thompson (1985) said they need large aquaria (over 100 gallons), can be conditioned to take prepared foods, grow quickly, and are highly suitable for outdoor ponds. Biologists at the Waterways Experiment Station in Vicksburg, Mississippi, kept small (3-5 inch) wild-caught Goldeye in large (300-liter and up) laboratory aquaria with good results. Initially, the nocturnal Goldeye were sensitive to bright light and fed only at night; after six months in captivity feeding occurred at all times of the day. Foods included feeder minnows, large flake food, frozen bloodworms, chopped earthworms, shrimp and clam chunks, live mealworms and crickets, and cooked squashed peas, and were usually taken mid-water or near the bottom of the tank. Two prey fishes were conspicuously avoided, even by hungry specimens: live Western Mosquitofish (Gambusia affinis) and live young-of-year Bluegill (Lepomis macrochirus), presumably because of the former's surface-hugging habits and the latter's fin spines. Like other pelagic (open-water) fishes, goldeye swim continuously.
At the Mississippi Museum of Natural Science in Jackson, Goldeye and Mooneye are kept in a large exhibit with other large Mississippi River fishes (e.g., Pallid Sturgeon, Paddlefish); the fish are hardy following some initial handling-related mortality, and eat the same "plankton cocktail" prepared for the Paddlefish.
According to Fernet and Smith (1976), both wild and captive Goldeye are not particularly gregarious. Their population density in one Canadian delta was estimated at one fish per 50 sq m (538 sq ft); likewise in the aquarium, Goldeye prefer to keep a space around themselves, and nip and chase away other Goldeye that get too close. Metabolism may play a role in aggressive behavior. In their study aquariua, Fernet and Smith found that females are more aggressive than males, and that smaller Goldeye are more aggressive than larger ones. It's hypothesized that female and smaller Goldeye have higher metabolic demands and therefore more vigorously defend their feeding territories. Interestingly, Fernet and Smith were able to subdue aggressive behavior by adding more adults to each tank. With less territory to defend, adult Goldeye didn't both to battle it out; instead, they formed a peaceful school.
Clearly, there is more to learn about the care and behavior of captive Mooneye and Goldeye.