Fish Nutrition & Diet

Every aquatics department should carry an assortment of food that will appeal to a wide variety of fish species.


Customers will frequently ask what they should be feeding their fish. To answer this question, first ask what species they are keeping. Once this is determined, ascertain how many times a day they are feeding. Then ask what food they have been feeding. On rare occasions, I have been able to say, “You are right on target, keep doing what you are doing.” Usually, however, I say, “You are not feeding often enough,” or “You are not feeding a wide enough variety of foods,” or “You are not feeding the proper foods for the fish you are keeping.”

Premium flake food is all that many fish will need to survive in the average community aquarium. However, variety is important to fish, just as it is to humans. Fish should get used to eating frozen food, since it offers this variety. There are many items offered in frozen form. Among my favorites are brine shrimp, bloodworms, mysis shrimp, krill, spirulina algae, beef heart, squid, daphnia, mosquito larvae and the popular glass larvae. Many frozen specialty diets are also available, such as shark, (marine) angels, discus and trigger formulae. I recommend at least one type of frozen alternative to flakes.

Another option is pelleted food. Pellets don’t leave the clouds of small, uneaten food particles that often result from feeding flakes. Pellets come in a wide variety of sizes, so they can accommodate fish from one inch to one foot in length. There are even large pellets for such fish as arowanas, pacu, Oscars, shovel-nosed catfish and, of course, goldfish and koi. Pellets may sink or float, and this is a bonus since substrate feeders need to get their fair share of the food being offered. Remember, every fish has a specific feeding zone, even though many aggressive feeders will chase food no matter where it is.

Live Food
If a store sells even a moderate selection of predatory species, it will be necessary to carry live feeder foods of various types. Since not all predators are large, stock small, medium and large live foods. From the trade, you can obtain brine shrimp and black worms. Some wholesalers and most goldfish farms sell feeder fish–goldfish in three sizes, guppies and rosy reds. Companies that supply live food for fishermen usually offer red wrigglers (earthworms), night crawlers (larger earthworms), shiners (cold-water minnow species) and minnows (usually killifish of a variety of species). It is also a good idea to carry ghost shrimp as feeders.

Almost all live feeders must be kept cool–which means chillers on holding vats and refrigeration for black worms and night crawlers. The other two live food items that a retailer might stock for fish are mealworms and crickets. Both have substantial exoskeletons, so they are best fed only to large fish that can chew them up sufficiently in order to digest them properly. If you carry live birds, small mammals and reptiles, you probably already stock these items as live food. Otherwise, it might not pay you to maintain them just for fish customers.

Live food used to be considered a “customer service” product that brought little profit to the retailer. This is no longer true, and since the big-box stores do not stock live foods, it is more important that pet specialty retailers do. These foods certainly have a shelf life, so carefully gauge how much is bought at a time. The double benefit is that they can be fed to the fish in the store. For this reason, very little should go to waste.

Every now and then, it’s a good idea to put common live foods on sale and advertise this in the store. This encourages people to try live foods–perhaps for the first time. In fact, giving away free samples to first-time users is something I strongly endorse.

Feeding Times & Quantities
It’s really difficult to convince people that tropical fish can be fed every four hours or so. Most pet shops recommends that fish be fed once or twice a day, but why be so conservative when the majority of fish can metabolize their food in two hours? The more often fish are fed, the faster they will grow–and the more fish food the store sells. Pretty soon, the customers’ successes will inspire them to purchase larger fish tanks. It’s a win-win situation.

Some people have a difficult time judging how much to feed their fish. This is really a learning experience that should be mastered in no more than a few feedings. When fish are grossly overfed, it is always a good idea to remove the excess food immediately. It can be siphoned off or netted out. Food left to decay on the substrate will rapidly raise the ammonia level and may initiate a bacteria bloom that will cloud the water. I believe most people tend to underfeed rather than overfeed. This results in weight loss and health problems due to inadequate diet. Fat fish are generally happy fish.

Most commercial fish foods are reasonably good for fish. The same cannot be said for foods marketed to people. A few energetic hobbyists may make up their own foods, but this practice seems to be falling out of favor. However, gaining popularity are refrigerated liquid products to feed live corals. Small, virtually microscopic food particles are held in suspension, and the contents must be vigorously shaken before being introduced to tanks. Various foods target different varieties of coral feeders. If the store has a substantial reef clientele, this type of food should be stocked.

There is no doubt that the fish food category in pet shops is ever expanding. It is becoming more diversified and more sophisticated. Many customers will require assistance in selecting fish foods. A common-sense approach is to keep prepared foods for tropical fish, marine fish and cold-water fish in separate areas. And keep koi pellets (both bagged and self-dispensed) in the pond department. This will serve as a silent guardian to prevent novices from selecting inappropriate products for their fish.

Edward C. Taylor has been in the pet industry for over 30 years as a retailer, live fish importer and wholesaler, and fish-hatchery manager.

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