That Reptile Blog – Reptile, Amphibian and Exotic Pet Care and Information

In Part I of this article we discussed the origin and current state of the problems associated with the long term use of goldfishes as a staple food for reptiles and amphibians.

Bait and Tropical Fishes

Fathead minnows, golden shiners and related fishes are preferable to goldfishes as a reptile and amphibian food, and may be used as dietary staples where appropriate. They are generally raised in outdoor ponds or wild-caught, and have fed on a variety of invertebrates, plants and other natural food items. This renders them a highly nutritious food item.

Whenever possible, you should alternate the species of fish offered. This is especially important for water and tentacled snakes, mata mata and alligator snapping turtles, Surinam toads and other species that feed primarily upon fish. Many common pet trade tropical fishes are nutritious and easily-reared, including swordtails, platys, guppies and mollies.

Food Market Fishes

Food market fresh water fishes (i.e. Tilapia and catfish), especially those which can be obtained whole, are another useful option. I fed the Bronx Zoo’s gharials (large, piscivorous crocodilians) on trout for many years…but that cost upwards of $1,000/month – 20 years ago!

Collecting Native Fishes

Where legal, you can add vital nutrients to your pets’ diets by collecting freshwater fishes via seine net, trap or pole. I always remove the dorsal and pectoral spines of catfishes, sunfishes and other well-armed species, just to be on the safe side.

Fish and Vitamin E

The Vitamin E question has also been investigated…I’ll write more on that in the future. For now, please be aware that frozen fish of any kind, used as a dietary staple for crocodilians and turtles, has been implicated in Vitamin E and other deficiencies. Marine fishes, frozen or fresh, seem to block vitamin absorption when fed in quantity to fresh water animals.

Further Reading

I must say that, food considerations aside, I like goldfish! Please check out our blog article Carnival Fish for some interesting background on their habits, care and long history as pets.

Concerns over the use of goldfishes (Carassius auratus) as a food item for reptiles and amphibians have long been recognized, yet there remains a bit of confusion on the topic. References to Vitamin E deficiencies in animals kept on fish-based diets, a separate problem entirely, often further clouds the issue. Prompted by recent comments on our blog, I thought I might address the subject in this article.

Goldfishes and Large Pets
The controversy is important because goldfishes are the least expensive and most readily available “feeder fish”. They are also available in a wide variety of sizes, allowing owners of large reptiles and amphibians to offer their pets a whole fish, and a more substantial meal than a large golden shiner. This is preferable, from a nutritional standpoint, to feeding cut pieces of a Tilapia or other large food-market fish.

A Valuable Resource for Live-Food Specialists
Goldfishes are also quite hardy and usually remain alive when introduced into an aquarium, even when subjected to large temperature changes (drastic temperature changes quickly kill other typical feeder fishes, such as golden shiners and fathead minnows). This allows us to more easily feed aquatic live-food specialists, such as mata mata turtles and tentacled snakes, and American bullfrogs and other large amphibians.

I once cared for a large, wild-caught alligator snapping turtle that refused to eat fishes unless, as in nature, they investigated his tongue’s “fishing lure”. Goldfishes adjusted so well to the exhibit’s water that they would try to eat the turtle’s worm-like lure in short order.

The Origin of the Goldfish Problem
I was fortunate in having been involved in the specific incident that led to the discovery of the nutritional problems associated with goldfish-based diets. During my early years at the Bronx Zoo, it was noticed that mata mata turtles (Chelus fimbriatus) that were fed solely upon goldfish thrived for about 5 years, and then died suddenly. The odd phenomenon, it turned out, was not limited to the Bronx Zoo, and had occurred in several other collections.

Necropsies of the turtles revealed liver and kidney damage, and problems indicative of Vitamin A overdose (this last was later disputed, and has not been proven conclusively).

Using Goldfishes
Experience has since established that goldfishes may be safely fed to reptiles and amphibians on an occasional basis, i.e. once monthly, but should not be used as a dietary staple.

Another Concern?
Some years ago, I came to learn that some commercial goldfish farms raised their stock largely on chicken droppings supplied by local poultry farms (goldfishes, it seems, are quite hardy…and goldfish farm owners equally resourceful!). I do not know if this is still the case, but often wondered about the possibility of Salmonella contamination. I’ve never run across or read of a problem…but looking into it might make for an interesting project.

Further Reading
Please check out the following article for another experienced turtle keeper’s view on goldfishes as a food item, and for a description of the mata mata turtle’s unique strategy of “herding” fishes and other prey.
http://www.tortoise.org/archives/matamata.html.