BREEDING Top tip
Maintaining optimal water quality is absolutely essential for successfully rearing koi fry. Carrying out a full range of water quality tests on a regular basis is the only sure way of keeping an eye on water quality – remember that the tiny fry are extremely sensitive to deteriorating water quality, and the environment of the rearing tank can be a challenge in which to ensure that water quality doesn’t suffer. Good hygiene practices need to be observed, including the removal of any food debris, and regular water changes will be required.
Cuttlebrook Koi Farm fry
Sanke fry 8 weeks old, second selection
yolk being able to swell the tiny stomach of the fry). Several days after hatching some Artemia
nauplii (the newly-hatched stage of brine shrimp) can be supplied. A few days after this (at around two weeks of age), some extremely finely ground flake food can be offered, or some of the commercially- available fry diets. Feeding will need to be carried out on a
very regular basis, ideally several times a day. In addition you should note that variety is extremely important. It’s worth attempting to culture infusoria (tiny aquatic beasties such as protozoans) as well as providing a supply of Daphnia to the developing fry.
developing koi When the fish reach about three weeks of
age, patterns and colours will start to develop. After about a month from hatching the
koi, which are now known as fingerlings, may be around 35mm in length, and to all intents and purposes look just like miniature versions of the adult fish. They will need to be moved on to a
It’s tempting to try and grow on all the available fry, but this can lead to problems
52 KOI CARP
suitable grow-out system. This could be a larger vat, or preferably even a pond, provided provision is made to pamper them suitably and keep predators away.
culling It’s tempting to try and grow on all the
available fry, but this can lead to problems. Certainly commercial breeders will, from six weeks post-hatching or so, be actively culling
Further information:
For more information about Tetra’s products and services go to
www.tetra.net.
Shiro Utsuri fry
to achieve the most desirable individuals. Culling is often cited as a controversial
welfare issue in the hobby – but is this accusation fair? Breeders will, over a few weeks post-hatching, cull well over 90% of the fry which hatch from a spawning. It needs to be remembered that it is, in practical terms, impossible to rear all of the fry – one female koi will lay many thousands of eggs, and the hobbyist and commercial breeder can’t realistically grow them all on. In any case, many of the tiny fry will be deformed or exhibit stunted growth or other developmental abnormalities, and have little chance of survival. Attempting to be too ambitious with the
number of fry to be reared is invariably a recipe for disaster, even if the sentiments behind such an idea are admirable. Finally, one of the factors that needs to be considered in this debate is the number of fry which would survive from completely natural spawnings if ‘Mother Nature’ had her way – it certainly wouldn’t be many!
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