Koi Fry Growth
Koi fry growth is something that every koi breeder should take seriously, and will help establish koi into strong, healthy specimens. When koi fry first hatch they will generally seek shelter and hide in any cover they can.
Spawning ropes can be used as a place for the fry to hide. Koi fry have a sticky patch on their head and can attach themselves to the rope. At this part of their life cycle they have no bladder, mouth or vent. They are able to breath by absorbing oxygen through the fine blood capillaries that surround the yolk sac.
It is very important to make sure the water has a good supply of oxygen as a lack of oxygen could result in poor koi fry growth or mass mortality.
The koi fry have only one fin that circles the posterior end of their body. As the koi fry grow and feed on the yolk sac they develop paired fins, mouth and the rest of their organs.
After a few days the koi fry swim to the surface and take their first breath of air which is forced into their swim bladder. They then start to swim freely in the water and are often found around airstones. This is a good indication that they are now ready to feed.
When koi are first fed they do not have taste buds and so have to visually see their food. It is for this reason that they need to have food around them all the time. Care must be taken not to let the water become polluted. Hard boiled egg yolk is a good food to feed the koi fry for their first couple of days however this has very little nutritional value but helps to increase the size of their stomach. Brine shrimp can then be fed to fry for the first week to help with koi fry growth . After this the fry will eat powdered fish food and gradually be able to deal with larger pieces of food.
Water changes are crucial at this stage as the large amount of food can increase nitrate and ammonia levels. Tap water will need to be treated to remove the harmful chemicals like chlorine, plus the water will need to be aerated.
The koi fry can now be moved to a growing on facility but are still too small to be added to the main pond. Large koi fry will often eat the younger smaller koi fry and if this happens you should move the larger fry to a separate tank). At first koi fry need to be fed little and often, then as they get older they can be fed less food and less frequently. Koi fry need more food than a mature koi in relation to their size especially for optimum koi fry growth