There are two basic ways of approaching the feeding of aquatic animals. One school of thought holds that most fish and invertebrates should be given as much variety as is possible, while the other leans toward the use of standardized, prepared foods containing all or most of the animals' nutritional needs in one package. The main factors in guiding your decision in this matter should be the natural history and specific food requirements of the species that you maintain. Availability of the various food items will also be important, but you should, of course, avoid animals whose nutritional needs you will be unable to meet. In general, supplementation in the form of added vitamins and minerals is more important for captive animals being offered a limited number of food items than it is for those that receive a good deal of variety in their diet.

Great advances have been made in recent years in our understanding of the dietary requirements of captive fish and invertebrates. We are even beginning to grasp the subtleties of their requirements as concerns such important items as vitamins, minerals, and micronutrients. Along with this understanding has come an explosion in the varieties of prepared diets that are available to the hobbyist. Great strides were previously made in understanding the nutritional requirements of commercially imported food fish and invertebrates, such as trout, catfish, and clams. Much of what we have learned in those fields has been applied to ornamental fish and invertebrates and has provided the foundation for further research. In fact, the diets prepared for such commercially important animals are healthful dietary items for such relatives of those animals that may be kept by aquarists. Therefore, those who keep catfish would be well advised to use commercial catfish foods, and you will find that carnivorous freshwater fish often fare well on a diet consisting mainly of trout chow.

For certain species, foods such as trout or catfish chow or those specifically formulated for aquarium fish may provide all or most of the nutrition required for good health, and even for reproduction. Commercially available foods that fall into this category might include dry flake foods and pellets designed for use as staple diets for marine or freshwater fish. This would be especially true if the flake or pellet were fortified with vitamins and minerals. Unfortunately, a good deal of experimentation is required before you can determine if a particular fish can subsist on a diet comprised solely of flakes or pellets. Your best guide in this regard would be conversations with hose who have successfully kept and bred the species in which you are interested.

Aquatic animals that consume live food only may prove difficult to accommodate in captivity. Variety in the diet is often a key to success in maintaining such creatures. As has been mentioned earlier, many of these animals will accept whatever sort of live food you might provide, but they may fail to thrive without appropriate variety. Large cichlids such as the oscar, Astronotus ocellatus, for example, will readily consume goldfish throughout their lives. To remain in peak condition, however, these robust animals should also be offered other species of fish, shrimp, earthworms, crickets, and various frozen and pelleted foods. Fortunately, a wide variety of commercially cultured food animals are available to the aquarists today. See Chapter 17, devoted specifically to live foods, for further information.

One way to introduce dietary variety to animals consuming live or frozen foods is to insert tropical fish flakes or pellets into the gill flaps or body cavities of the food animals, or to inject liquid vitamins. This way, animals that are offered few food items in captivity will be supplied with important vitamins that might otherwise be missing from their diet.

One way to help ensure that those pets feeding upon live food are obtaining a balanced diet is to vary the species of food animal that is given to them. If, for example, you are keeping a pumpkinseed sunfish, Lepomis gibbosus, alternate the species of fish and insects that you offer to it. For example, readily available species such as guppies and crickets can form the basis of the diet, with small minnows, shiners, earthworms, and moths and other such insects when available. Also, bear in mind that commercially raised food fish will provide different nutrients than will those collected from their natural habitats. Wild-caught food fish will generally have been feeding on a wide variety of invertebrates and plants themselves and are therefore a more complete food item to offer to your pets. Bait stores often sell various species of minnows and shiners that have been seined from outdoor ponds, where they had been feeding upon a fairly varied natural diet. It is usually a simple matter to contact the supplier of such fish and to ascertain from where the stock originates.

An important point to remember is that the diet fed to the food animals will influence the quality of the nutrition that they supply to your pets. This topic is discussed at greater length in Chapter 17, which specifically concerns live foods.