Fish of appropriate size are excellent food sources for predatory species. Many types of small-to medium-sized freshwater fish, including guppies, goldfish, fathead minnows, and golden shiners are sold by pet stores specifically for use as food fish.

Several species of freshwater live-bearing fish are very hardy and, if maintained properly, will produce large numbers of young that can be used as food for other pets. An advantage of maintaining a colony of such fish is that you will always be assured of a supply of food fish of varying sizes. Ideal candidates for captive breeding include guppies, mollies, swordtails, and platys.

Currently there are no marine species that can be easily bred in large numbers as a food source for other animals. However, the very fruitful mollies are, in actuality, brackish-water fish. When properly acclimated, mollies will live in marine aquariums and can be hunted by the inhabitants at will. This is an especially important consideration for those maintaining marine species such as anglerfish, which will often consume only prey that shows an interest in the angler's lure.

Guppies and similar live-bearers should be housed in a well filtered aquarium at a ratio of one male to every three or four females. At temperatures of 73°F to 77°F (22.7°C to 24.9°C), these fish will reproduce quite rapidly. Breeding success can be increased by feeding a well-balanced diet of tropical fish food flakes, pellets, and live foods such as brine shrimp and black worms. In addition to allowing for larger and more vigorous broods, such a feeding strategy will also greatly enhance the nutritional value of the food fish. Pregnant females can be readily identified by their swollen abdomens and should be placed in breeding traps. These devices hang within the aquarium and have a sloped, slotted false bottom that allows the young to escape the ravenous appetites of their mothers. Babies can be housed in the same aquarium with adults if provided extremely dense cover in the form of living plants or commercially available breeding grass, but in such situations you will likely lose a good number to predation.

The commercial suppliers of golden shiners and fathead minnows usually seine them from outdoor ponds in the southern part of the United States. Although these fish are fed a commercial diet, a good portion of their food comes from native plants and invertebrates. Animals consuming a well-balanced and fairly natural diet will likely provide your pets with good nutritional value. You should, therefore, consider using farmed or wild caught fish along with the other species mentioned above.

You may also wish to stop in at bait shops in your search for additional food animals for your pets. These establishments, as well as commercial dealers that advertise in the classified section of fishing magazines, often stock fish and invertebrates unavailable in the pet trade. Purchasing such animals will add important variety to the diet of your aquarium's inhabitants and may tempt reluctant feeders.

A wide variety of freshwater and marine fish suitable for use as food may also be seined or trapped in the local ponds, rivers, and oceans. As always, be sure to check applicable laws and regulations before collecting any fish.