Many old-time aquarists relied upon catching and culturing live foods to feed their fishes. This was mainly due to the fact that there was not the diversity of manufactured fish foods available. The live foods that became most popular were those that could be easily collected or cultivated. Up until the 1950's, keeping and breeding rainbowfishes in captivity generally required the routine collection of live food from streams and ponds or whatever the aquarist was able to find. Some of the items that were used included bloodworms, small garden worms, gentles (maggots) that had been purged in bran, pre-soaked wheat, barley or millet grains, and now and then, "coffee biscuit, vermicelli crushed small, occasionally varied with a little fresh food or gentles, and the various varieties of animalculæ."
The feeding of aquarium fishes was revolutionised with the invention of dried flake food by Dr. Ulrich Baensch, founder of Tetra Werke. Today, approximately 80% of aquarium hobbyists feed their fish exclusively with prepared foods, usually in flake, pellet or tablet form. Flake food is the most common form and is consumed by a wide variety of aquarium fish. Flake food is baked to remove moisture and create the flaking, thus allowing for a longer shelf life. Generally the more moisture a particular fish food contains, the more readily it will deteriorate in quality. However, since there are very few published reports on rainbowfish nutritional requirements or an evaluation of formulated diets on growth and fecundity, it is not known whether protein and carbohydrate levels of these diets are optimal.
Feeding live foods are not necessary, but if you have access to them then this is by far the best food that you can feed to your rainbowfishes. Aquarists who have been fortunate enough to discover pristine ponds inhabited by live foods generally keep them a close secret, and set out to collect them at dead of night, in order to keep them to themselves. However, the time required collecting live food from local ponds and streams and the risks of introducing pests, parasites and disease to a healthy tank are enough to make even the most avid aquarist question the desirability of such practice. What to watch out for are dragonfly larvae, hydra, leeches, planaria, snails, water beetle larvae, water tigers, and other carnivorous insect larvae. They may not bother larger rainbowfishes, but small fry have no defence against most of these pests. You can overcome all these problems by maintaining live cultures of cladocerans (zooplankton), copepods, mosquito larvae, drosophila, whiteworm, etc., at home.
Rainbowfishes are well adapted to capturing live cladocerans (daphnia, moina etc.) and will show an active response to this type of food, indicating that cladocerans are a very attractive food for rainbowfishes. Upon adding cladocerans to the tank, it is quite often the case that rainbowfishes will exhibit an immediate response that somewhat resembles a feeding frenzy. Live food is preferred over inert food by rainbowfishes, suggesting a moving prey item may stimulate or influence feeding preference. In the presence of both live food and a flake or pellet diet, rainbowfishes spend significantly more time feeding on live food than on inert foods.
Under aquarium conditions, rainbowfishes characteristically display a considerable range of growth rates, depending on conditions such as food, space, numbers, competition and water temperature. At present there is little information available concerning the quantitative dietary nutrient requirements of rainbowfishes under aquarium conditions, or regarding the nutrient requirements of the first-feeding larvae and broodstock of rainbowfishes. Despite this, and on the basis of 'laboratory based' nutritional feeding trials conducted to date, some generalised conclusions may be drawn regarding the recommended nutrient levels. Nevertheless, there are still many unanswered questions when it comes to the nutritional requirements of rainbowfish species.
Maintaining good health and growth in your rainbowfishes depends directly on the quality and quantity of the nutrients received through their daily diet. If the feed is not consumed by the fish or if the fish are unable to utilise the feed because of some nutrient deficiency, then there will be no growth. Without the right amount of nutrients, rainbowfishes may cease to grow, lose colour, stop breeding, and become susceptible to disease and, in certain circumstances, might even die. An undernourished animal cannot maintain its health and be productive, regardless of the quality of its environment. Rainbowfish keepers determined to raise and maintain the finest specimens must provide a nutritionally balanced diet for their rainbowfishes throughout their entire life cycle. Obviously, no single food will meet their needs at all life stages, and the best way to ensure that they are getting a well-balanced diet is to feed them as wide a variety of food as possible.
Under aquarium conditions the feeding of rainbowfishes normally has to rely on "unnatural" foods. Therefore, it is necessary to provide favourable aquarium conditions and careful feeding with specially formulated diets in an attempt to satisfy all their nutritional requirements. Rainbowfishes can be maintained on a diet consisting totally of commercial feeds such as flakes, pellets, and granular formulations. The well known brands have been formulated so that the basic nutritional content is at the proper levels. Such feeds however, need to be not only nutritious and palatable, but also capable of floating or sinking slowly. Rainbowfishes are primarily surface feeders so feeds that sink too quickly may become wasted in the gravel substrate. Over feeding can cause water quality problems, which can compromise fish health and create significant problems. Irrespective of the quality of these manufactured foods, they may not provide the complete nutritional requirements necessary.
Sometimes rainbowfishes can be encouraged to experiment with unfamiliar food items by withholding other preferred food items. This works well, for example, when feeding parboiled (soften) zucchini (a good source of B and C vitamins) for the first time. Simply withholding their regular food and offering the less familiar zucchini usually results in rapid acceptance (1~3 days). Similar strategies can be used to feed rainbowfishes homemade gelatine-based foods. Gelatine-based foods can also serve as an excellent carrier for oral medications, but the fish should be use to eating a plain (non-medicated) homemade diet before there is a need to use it as a means of delivering medication. As with many sick animals, the appetite is often significantly depressed in sick fish, and that is not the time to try and introduce an unfamiliar food item.
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