Although formulated foods play a significant part in the diet of many fish, especially in a typical community aquarium set-up, live foods can also fulfil an important function. Live food is a key component in the diets of certain fish that do not thrive on formulated foods alone, and, in some cases, can act as a breeding trigger (the increased availability of protein-rich live food improves the chances of survival for fry, so the adult fish are stimulated to reproduce).
Many of these live foods, such as tubifex worms or daphnia, are available in prepared form, typically freeze-dried or frozen, while some may be obtained fresh. If using fresh worms, store them in a cool, dark place in a large container of water; they will not thrive within the confines of a glass jar. When offering worms to your fish, use a special feeder that sticks to the side of the tank, allowing the fish to eat the worms directly. If you simply tip them into the tank, then only the bottom-dwelling species are likely to benefit.
Aquatic live foods
Another live food traditionally offered to fish are water fleas. Usually known by their scientific name of Daphnia, these are actually tiny crustaceans and not fleas at all. Be warned that if you collect these from the wild such as from a pond, there is a risk of infection, and you could also inadvertently introduce hydra to your aquarium. This would be particularly devastating if you have any fry because the hydra will kill them rapidly with their stinging tentacles. One way to avoid this is to cultivate the daphnia yourself, in an old tank or similar container outdoors, so that they do not come into contact with other aquatic life.
Daphnia are available from aquatic stores in plastic bags of water. If they have been kept in direct sunlight, this can kill them very rapidly, so you should check that the majority of them are alive. Tap the sides of the bag and you should see them swimming around with their characteristic jerky movements.
Tip the bag into a small tank or similar container as soon as you reach home. You can then sieve the daphnia out of the water as you need them and transfer them to the aquarium. This is much safer than simply tipping the contents of the bag directly in alongside the fish. Daphnia are also sometimes used for their laxative effect; you can add them to the water as a remedy if any of your fish show signs of constipation, with their droppings trailing in a strand from their vent.
Other aquatic live foods may be cultivated quite easily at home, using a bucket of water. This will attract gnats, for example, to lay their eggs here during summer. The eggs hatch into larvae which should be sieved out of the bucket then fed to the fish. As no other aquatic creatures are involved with this method, it is very unlikely that you will introduce any hazards to the tank.
Terrestrial live foods
A number of other live foods which have to be cultured rather than bought can be a valuable addition to the fish’s diet. Starter cultures of whiteworm (Enchytraeus) and similar species are frequently available through advertisements in fish-keeping journals.
Whiteworm
To culture your own whiteworms, first prepare a clean container with a lid, such as a margarine tub. Put in a small quantity of soil, then make drills in the soil with a pencil. Soak some bread in milk and poke this down into the drills. Divide up the starter culture, placing the worms on top of the food source, and cover them.
Transfer the culture to a reasonably warm place, ensuring that it does not dry out. Replace the bread every two or three days. After about a month, there should be enough worms to harvest. Separate them from the soil by tipping them into a saucer of water. You can then easily skim off the worms with tweezers and offer them to the fish in small quantities.
Fruit-flies
Fruit-fly (Drosophila) starter cultures are also available, which can be set up in large jam jars covered with muslin. Fruit-flies are especially appreciated by hatchetfish and other species that live close to the water surface. Try to obtain wingless fruit flies, because they will not escape into the home. Special feeding media are available, although you may also achieve good results by providing the flies with banana skins as a source of nutrients. To feed the fish, simply tip some of the flies directly onto the surface of the water. As with all live foods, do not add too much at once because leftover food will quickly pollute the water.
Earthworms
Another form of live food for fish that are available commercially are earthworms. Select the size carefully when placing your order, otherwise you will have to chop up the worms before offering them to your fish. In general, they are only suitable for larger species. It is best not to use worms directly from the garden, because there is a risk that they could have harmful microbes in their digestive tracts. If you do want to try using them, you should reduce this risk by leaving them in a moist container of vegetable matter for several days, in the hope that they will empty their digestive tracts.
Crickets
Various types of crickets are available in a range of sizes from small hatchlings upwards and so make a versatile live food. These are sold primarily for birds and reptiles, but may also be offered to fish. Feeding mealworms is less recommended, because their hard casing makes them relatively indigestible, although soft-bodied, white mealworms may be used safely.
Prepared live foods
Many live foods are available in freeze-dried or frozen forms. Although relatively expensive, these foods may prove especially valuable for conditioning fish prior to breeding. They are also very convenient because they may be stored indefinitely without refrigeration and they are much safer to use than the equivalent fresh live food. Freeze-drying removes moisture from a food so that it keeps very well, without affecting its palatability too much. Small worms, such as bloodworm, are dried and compressed into blocks, whereas large river shrimp are frozen individually.
Gamma irradiated foodstuffs are sterilized and then frozen; they should be stored in a freezer. To use this food, cut off small blocks with a sharp knife as needed, and thaw them before feeding to the fish. If you only need part of a portion, you may be able to shave off pieces while still frozen so you thaw only a small amount.
