Knowing how much to feed rainbowfishes without overfeeding them is a problem for most aquarists. A rule-of-thumb is to feed all the fish will consume in 5 to 10 minutes. Unfortunately, this method can easily lead to overfeeding. Rainbowfishes always seem to be hungry; you can feed them, and five minutes later they will look at you as if they are starving. This is because the fish have learnt to associate you with food and get excited when they see you.
It is necessary to understand about conditions in the wild to appreciate why rainbowfishes have this behaviour. Food is a limiting resource in nature and it is rarely available in excess quantities. The individuals that survive are those best able to acquire this limited resource. Rainbowfishes are opportunistic and feed whenever they can find food. It is neither necessary nor advantageous in the wild to control their appetite. Therefore when rainbowfishes are kept in an environment with unlimited food, they do not know when to stop feeding.
The amount of food required depends on the type of food, aquarium conditions, and individual fish. Smaller fish consume a higher percent of their body weight per day than do larger fish. In the wild, adult rainbowfish may go for days without food, whereas, newly hatched larvae need to feed continuously. Research has shown that small fish will grow faster if fed three or four times a day. Feeding several times a day can also reduce problems of feeding dominance among fry of different sizes. Multiple feeding's spread the waste load on the biofilter and help prevent sudden decreases in dissolved oxygen.
Most rainbowfishes require a feeding ratio of 5-10% of their body weight daily and ideally, should be fed this amount in four or five smaller feeding's during the day. However, knowing the weight of your fish is not practical, so feed sparingly, supply enough to give three to five minutes of continuous feeding per meal. It would probably be a good idea to miss feeding them for a day occasionally as well.
Water temperature directly influences the desire of fish to feed. Rainbowfishes are poikilothermic animals, which means that their body temperature is largely equated with that of their surroundings. When temperatures drop below 20°C, rainbowfishes will consume less feed so reduce the feeding rate accordingly. During cold weather conditions, it is best to feed late in the afternoon when the water temperatures have had a chance to elevate during the day.
Rainbowfishes require a highly nutritious diet in order to maintain spawning condition and produce large numbers of eggs. Nutrition also plays a significant role in growth, colouration, and the overall health of rainbowfishes. 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.
Research is finding that diet strongly affects not only fecundity but also the biochemical make-up of eggs and sperm as well as the growth rate and survival of larvae. Due to advances in the aquacultural industry, the nutritional requirements for feeding commercial food fish species are well documented. Nevertheless, there are still many unanswered questions when it comes to the nutritional requirements of rainbowfish species.
The use of a good quality food will provide the fish with all the nutrients that they need to remain healthy and to grow. However, you should note that even good quality food will deteriorate if improperly stored or kept too long. Storage time for most commercial fish foods will vary depending upon environmental conditions; however, as a rule of thumb, 90 days is normally the maximum safe storage time for fish feed. Fish foods should be stored in a cool and dry place (refrigerator), and used within 30 days of opening, particularly in hot, humid climates. Never feed mouldy, discoloured or clumped feed. Moulds on feed may produce aflatoxins, which can kill fish. Only buy large containers of food if you have a large number of fish.
For general aquarium maintenance, most of the commercial feeds are adequate. However, it is advisable to give your rainbowfishes an occasional feed of green food. A lack of green food is detrimental to their health. The best, because it is the most natural, is duckweed. When this is not available good substitutes are boiled and finely chopped spinach or zucchini.
Duckweed has higher concentrations of the essential amino acids, lysine and methionine, than most plant proteins and more closely resembles animal protein in that respect. Cultured duckweed also has high concentrations of trace minerals and pigments, particularly beta-carotene and xanthophyll that make duckweed an especially valuable supplement for rainbowfishes. The fairly high concentrations of these pigments deepen the overall body colouration of rainbowfishes. The smaller species like Wolffia and Lemna are better for rainbowfishes and most will eat it avidly.
Duckweed growing in nutrient-poor water typically ranges from 15 to 25 percent protein and from 15 to 30 percent fibre. Duckweed grown under ideal conditions and harvested regularly will have a fibre content of 5 to 15 percent and a protein content of 35 to 45 percent, depending on the species involved.
In a well-established aquarium the fish will always fine some green food among the aquatic plants, but a feed of duckweed, or spinach, about once a fortnight is to be recommended. If duckweed is taken from native waters it should be thoroughly cleansed before giving it to the fish. Failure to take this precaution may result in undesirable parasites being introduced into the aquarium.
To keep rainbowfishes in foremost breeding condition you should be aware that nutritional deficiencies may exist in prepared foods. An ideal aquarium diet for rainbowfishes could include foods such as live and frozen daphnia, bloodworms and other aquatic invertebrates, chopped fish or shrimp, blanched zucchini, spinach and duckweed. Spirulina-based foods, flake, and bite-sized pellets designed for ornamental fishes are also acceptable. Avoid feeding large amounts of dried feeds developed for the aquaculture industry, which can cause health problems in rainbowfishes over the longer term.
Feeding is the best opportunity for you to observe the overall vitality of your fish. Poor feeding response is a signal that something has gone wrong in the aquarium. Check all aspects of the system particularly water quality, and look for signs of disease or stress.
Whatever choices you make regarding feeding your fishes, remember that variety is not only the "spice of life", but is the best way to provide them with the essential nutrients to give energy and build tissue. A reasonably knowledge of the function of foods and feeding will therefore help in the choice of the most suitable food available for your rainbowfishes or in formulating your own mixture.
© Copyright Adrian R. Tappin
Created July, 2005.
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