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The essential requirement for successfully raising rainbowfishes is the implementation of a suitable feeding regimen for the larvae. Using the following feeding program, the survival of rainbowfish larvae can be as high as 80~95%. Begin feeding with small amounts of infusoria. The term infusoria is a collective name for many micro-organisms and can include paramecium, unicellular algae, ciliates, bacteria, protozoans, desmids, rotifers, and a host of other small organisms. Rainbowfish larvae will also benefit from the addition of small amounts of greenwater (phytoplankton). It is well known that phytoplankton contain an array of essential nutrients that help the growth of rainbowfish larvae. Providing greenwater with infusoria as food for the newly hatched rainbowfishes has several advantages. The larvae are easily able to switch to different sized prey, a feature not present in monocultures of organisms such as rotifers or brineshrimp. Greenwater also enables the "infusoria" to feed on resident algae and microbes, thus retaining their nutritional value for greater periods of time. Feed 5~10 ml (per 20~50 fry) of infusoria suspension three or four times per day. You can tell if they are feeding well as the larvae should have nice "swollen stomachs" after feeding.
Starting on day 7 to 14, depending on size, you can begin introducing small amounts of newly hatched brine shrimp nauplii and/or microworm. The feeding of rainbowfish larvae on the brine shrimp nauplii will be very inefficient at first; so add just enough such that the fry will encounter a small "cloud" of nauplii for a few minutes in the water column. Do this each time you feed brine shrimp nauplii to older fish. Observe fish closely after feeding. Once you can see that the fish have been successfully taking the brine shrimp (their stomachs will be orange), add more with each feeding. Never add so much brine shrimp that more than 10~20% of it dies in the tank. Brine shrimp will accelerate growth so it is important to commence feeding as soon as possible. The smallest larvae will continue to eat the infusoria while the larger ones will start feeding on the brine shrimp nauplii or microworm.
Gradually increase the proportion of brine shrimp nauplii or microworm and phase out the infusoria - this should be around day 14 to 21. Continue feeding the juveniles with brine shrimp nauplii and microworm three times a day. Do not overfeed, a good rule of thumb when feeding brine shrimp nauplii is that they should be mostly eaten after about 20 minutes, at which point the babies will have nice red stomachs. When weaning fish to a new food, introduce 10% of the new food daily while reducing the same percentage of the initial food until 100% of the new food is accepted. Commence feeding adult foods as soon as the juveniles are big enough to eat it and feed them often (at least twice daily).
In addition to microworm or brine shrimp nauplii feed them once each day with a sprinkle of powdered spirulina. Spirulina is an algae-derived food rich in protein, carbohydrates, amino acids, vitamins and minerals, and essential fatty acids. Spirulina powder is available from most health food stores. The powdered microalgae Chlorella and Dunaliella that are sold in most health food stores can also be used as aquarium food supplements.
The growth rate of the rainbowfish larvae is generally slow, with little variation until around 14 days. After that time growth rates increased. However, considerable variations in the growth rate of juvenile stages of rainbowfishes have frequently been observed. Lack of food during early development leads to appreciable variation in growth (length), if compared to larvae offered food ad libitum. Adequate food and suitable temperature generally results in higher growth rates. Beside effects on growth, a decline in mortality between fish receiving small amounts of food and well-fed fish has also been observed.
It should be noted that the hatching of eggs might vary, resulting in the presence of larvae at different stages of development. As the larvae increased in age, the variation in length between individuals also increased. Thus, different factors can increase the duration until sexual maturity is reached. If you have a batch that differs greatly in size, you will often find that the smaller ones are females. To raise an entire spawning, you may have to sort the growing fish by size, as the larger ones will eat their smaller siblings or repress their growth rate. Size grading separates the faster and slower growing fish. When these smaller fish are transferred to another tank, their growth rate is no longer negatively impacted by the faster growing individuals. They should increase their growth rates to compensate for the initial retarded growth rates that developed during the nursery phase. In addition, a high fish load can retard the growth of juveniles, probably due to release of growth-inhibiting substances. For maximal growth keep the number of fish per aquarium low and avoid overcrowding.
General maintenance includes daily siphoning of the aquarium to remove any uneaten food and faeces, and 25~50 percent waterchange at least one a week. The continued growth and development of the fish will vary from one hobbyist to another and is largely conditional upon captive environmental conditions such as temperature, water quality, and feeding regime. Sexual differences begin to appear between 9 and 12 weeks after hatching with sexual mature at 6 to 12 months.
© Copyright Adrian R. Tappin
Updated December, 2008.
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