How to Sex Kois
Once the Koi go beyond three inches in size, the testes in males and ovaries in females begin to develop. The ovaries are much larger organs than the testes. Females are usually easier to spot, as the tummy of a mature female Koi is normally plump, whereas males stay streamlined and more torpedo formed. So wait until your Kois are bigger than about three inch before you start sexing them.
How Kois are Spawning
When males are ready for spawning, they develop breeding areas on the top and pectoral fins, principally along the bones of the fin rays. These mating areas appear as fine raised spots and could be mistaken for white Ichthyophthirius. The areas are most profuse on the pectoral fins, where they are quite rough to the touch and arranged in fairly regular rows. These are used during breeding, when the male nudges the female with his head and fins to induce her to spawn. Koi in fish ponds will normally spawn in the early summer season. A drinking water temperature of 68° is ideal, although Koi will sometimes spawn at a temperature of 63°. As the water in the fish-pond warms, the Koi will try to spawn ‘en masse’. This is known as flock spawning and, although it can produce very healthy offspring, the quality of the patterns and color are usually poor.
The female Koi deposits her eggs, approximately 100,000 per kilogram of her body weight, within the pond walls, floor and on any vegetation. Regrettably, it is very hard to collect eggs deposited in this random manner in order to incubate them in a setting where they will not be eaten by their parents or attacked by parasites. If remaining to their own devices, a few of the eggs will hatch and you will then gather the offspring and raise them within an aquarium.
You can, however, ensure the survival of a greater number of eggs by placing artificial spawning ropes in the pond. The Koi will deposit their eggs on these in preference to using the hard fish pond wall. To make these spawning ropes, cut 4 foot lengths of ½” heavy nylon-fiber rope and thread these between the strands of a 4 foot piece of the same sort of rope. As the Koi start preparing to spawn, you will observe men chasing a female, nudging her aspect with their mouths. The feminine will occasionally stop and suck at the sides of the pond in an attempt to clean an area on which she can deposit her eggs. This is the time to softly lower the spawning ropes into the fish-pond. Spread out the coils of rope into a fanlike shape and anchor them to the side of the pond.
Try to avoid disturbing the fish before and during spawning, but keep a careful attention on them, as the males may bully some females. If this happens, remove the feminine and place her in a separate pond. Koi may prefer to spawn around dawn but they may also spawn throughout the day, when they have finished spawning, the females hang mind down, respiring seriously, and the other seafood will become less excited. Lightly take away the spawning ropes and carefully place them in a vat for incubation. Koi are not good parents and if you don’t remove the eggs from the fish pond quickly, they will start to eat them. Immature Koi could also eat the eggs, so if you want to rear them, you should individual the spawning Koi from others in the fish-pond.
How to Incubate Koi Eggs
The incubator should have a reasonable capacity. A water storage tank about 100 gallons is ideal, and should be made of non-toxic materials. It will need a valve-operated drinking water inlet point and an shop with as large a surface area as you can screened with a very fine plastic mesh. Nylon stockings are an adequate alternate although they are less powerful.
Lay down the ropes out in the container water which has been treated with malachite green solution to stop fungus from attacking deceased eggs and growing illness to living eggs. Position the ropes in some way just at 2” below water level. Do not add any more water at this stage, but place an air stone on the floor of the vat to gently and continually aerate the water, as developing eggs need plenty of oxygen. When you begin to see the growing Koi’s eye in the egg, after one or two days, run a fine trickle of water in to the incubation vat. The day before the Koi hatches the eyes in the egg will have a sparkle to them. Soon afterwards, the young Koi will start to wriggle then, gradually, over the next few hours, it will break out of its ‘shell’. It will take three to four days for the Koi eggs to develop and the fry to hatch at temps of 68°-7l°. Koi fry can develop at temperatures as low as 63°, in which case their incubation will need five or six times, or as high as 77°, that will decrease their hatching time. However, there is a greater chance of the fry being deformed at such extreme temperature ranges.
Koi Eggs and Fry
When the fry have hatched, they will instinctively seek shelter and conceal in any cover they can find. The spawning ropes are perfect for this. Using a special sticky pad on their minds, the fry attach themselves to the ropes’ fronds, or to the vat wall structure. At this stage in their development, the young Koi have no swim bladder, mouth or vent. They breathe by absorbing air through the fine blood capillaries that surround the yolk sac, which continues to be attached to the gut. It is essential that there is a lot of oxygen entering the water at this time, as a reduction in the number of dissolved air in the incubator could lead to mass mortality.
The Koi fry have only one fin, which encircles the posterior end of your body. As the Koi grow, feeding on the yolk sac until all the yolk is utilized, they develop paired fins, a mouth and other organs. After two or three days, the young Koi swim up to the surface and take several gulps of air, which they force into their swim bladder. They then start to swim freely in mid water, usually congregating across the air stones, a sign that they are ready to be fed.
First Feeding
Koi fry at the “swim up” stage do not have any developed taste buds and so must detect their food by sight. Therefore they need to have food all around them. Hard-boiled egg yolk is an ideal food for the first day or so. This has very little eating value, but will raise the size of the abdomen. Newly hatched brine shrimp larvae are also a good food source for young Koi fry. Start feeding the brine shrimp when the Koi are about one week old. After another week or so, the Koi will be ready for a mash diet (the powder dust that is still left after the making process of fish food). From this time onwards, feed the Koi food of the size that can be taken by the smallest seafood in the vat.
You will need to remove accumulated debris and waste frequently during this first feeding stage. A siphon made from aeration tubing is well suited for removing settled and suspended waste from the incubator, and an old toothbrush is useful to clean the electric outlet screen. You should also add fresh drinking water regularly to the vat to remove nitrates and ammonia. Tap water which includes high concentrations of chlorine should be aerated before it is added to the vat, to allow the chlorine to evaporate. After three or four weeks, the fry will have grown to ¼” to ½” and will be needs to take larger quantities of more generously sized foods.
Growth
At this time, put the Koi to a growing-on facility, such as an aquarium, tank or pond. Watch the young Koi carefully, as cannibalism is not uncommon. If you suspect this, remove any bigger fry to another fish tank. You are able to temperature this to 68°-77° to allow quicker growth rates, but be careful; if Koi develop too fast, they lose their color. One month old Koi need to have about five percent of their bodyweight in food and really should be fed little and often. As they grow Koi need less food, about two percent of body weight 6″ or larger. The size of pellet food is critical; not all fish develop at the same rate and it is too easy to look at the larger Koi and select the pellet size to suit them, forgetting the smaller fish. Sadly, Koi that are nearer to the common carp in appearance grow faster than the prettier Koi. This is because Nishikigoi are highly inbred, that is these are mated with other Koi to which they are closely related, such as either parents or siblings, and as with any highly inbred animals, Nishikigoi aren’t as hardy as their undomesticated counterparts.
