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Breeding koi

Selecting the parents for breeding
For the novice breeder the question of selection can be frightening and sometimes bewildering. You can, although it's not advisable, breed koi when they are too young. The best results come when the female is at least 4 years old and a male at least 3 years old.

The reason being is that the female would be of a good size and in good condition which would let her carry many thousand large, quality eggs with a good yolksac. The larger the yolksac the larger the fry and the quicker they will eat microscopic food so the faster they will grow.

It is an advantage to use a large koi of 4 years as they have better ability to cope with the sometimes many hours of the spawning cycle. As a novice some people get quite upset over the rough handling of the female by the male or males when they are in the breeding tank.

It is quite common for the male to completly lift the female out of the water and push her around the pond sideways. After she is just about empty and has deposited her eggs on the breeding material, she will hang her head and stay in a corner exhausted and some will think she is dead. Still the males will chase her for more action, then when she has no more interest in laying all of the koi in the pond will start eating or sucking at the eggs.

But I am getting ahead of myself lets go back to the selection of parents.

We will leave the exotic koi alone. For the novice, all he or she wants to do is to put down a spawn of their own, so we will only talk about two lines of koi. They are: the ones with white skin - line 1, and the ones with black skin - line 2. Then we will throw in their metallic cousins!

White skin koi usually have white pectoral fins but some may have a few black stripes, as with the sanke, and either – red, orange and/or black patterns.

Some white skin line examples: kohaku, sanke, tancho, (shiro, ki, aka) bekko.

Black skin koi usually have black in the joint of the pectoral fins and either - white, red, orange or a mixure of all in the pattern.
Some black skin line examples: showa, (shiro, ki, hi) utusri.

Looking at the photos below: left is a female showing a fat belly (eggs) and the right is a male, slim like a torpedo.

We can use a male metallic koi to breed with both lines if you don't have a mate of the same line. This will make the offspring look like their parents but with a metallic sheen, this will put the offspring into the Hikari class (which means metallic). Some of these hikari are beautiful to look at in the sun.

The above applies to both full scale and doitsu types.

It is advisable to keep a log or record of your mating as you will need it later on. Some things to consider in your log - if the male does his job (stimulates the female), if the female is a good layer (utilises breeding material), and if they were a good match. It is especially important later when you are culling, to keep a record of how successful the mating was (colour, pattern, hatch rate etc.), then you will have a reference of parents and offspring for future spawns.

Oh and don't forget to log who the parents were (I give each of my koi an ID number)!

Do not breed koi with deformities, only breed with healthy koi.


Preparing your breeding stock
If you have room, it is preferable to separate your breeding females from the main pond to a second pond with the same main pond water running through it. Even if you only have one brood female add one or two more females for company as she will loose condition being alone. Never lift a brood female out of the water using a net. Slip her into a plastic bag to move her, this way she remains buoyant in water. If you have enough room you can also keep the breeding males in another pond. The reason for isolating the females is one morning after rain you may find that the horny males will pack rape her and any other females that are full of eggs. To bring a female into condition for breeding I use soft pellets, brown bread and vegemite and tiger worms, but no carbohydrates like pasta, rice etc. For males - tiger worms, brown bread and vegemite, pasta, rice and cereals like Nutri-Grain.

Peparing the raising pond

This can be done in two ways:- - Growing green water and Daphnia in the same pond, and/or - producing Daphnia and green water in separate ponds. All this needs to be done 2 to 3 weeks before you start breeding depending on location of the pond as it needs full sun. After the fry have hatched and consumed their egg sack, they will naturally start looking for food. This will be something small like micro-organisms which are found in green water (Infusoria), which is the bottom of the food chain. As the fry grow they look for more substantial food. This includes Daphnia (water fleas) of various sizes. Daphnia also feed on the Infusoria. I use two containers for this, one - the hatching pond is cleaned and dried for a few days and then refilled with clean tap water to a depth of 30 cm (do not use the filter). (The fry cannot survive the pressure created by water over this depth). Let it age and add 1 teaspoon per 450 lts of complete garden fertilzer and let the water go green. At the same time I fill some 300lt containers with pond water and add some chook poo and dry, boiled hay. This will start my water fleas growing which are a good source of live, natural food for fry. Check and adjust your pH to as close to neutral as possible. And cover the pond from nasties!

Raising daphnia (water fleas)
You cannot have too many Daphnia as the fry will feed on them for months.

It is best to cultivate Daphnia in a tank or pond with a large surface area in full sun and covered with fly mesh or shade cloth. Make sure they have an air supply, they are heavy users of oxygen.

If you see the daphnia turn red then this is a sign that there is not enough oxygen in the water. Either add an extra air stone or thin them down BUT do not take more than 1/2 the stock.

If you have some or you get a bag of daphnia from a koi mate, they can survive over winter. So do not empty out the tank completely as the eggs will be on the bottom.

To start a culture, throughly clean your container, add treated or fresh water and let age as chlorine will kill them - as will other koi medications! Add 1 level teaspoon of complete garden fertiliser per 450 lts and let the water go green. To aid this you can boil some hay or hand cut grass, dried and boiled when cold add the water you boiled and the hay (best put in a stocking or alike) to the tank.
Another way is to put a handfull of chook poo per 300 lts in a stocking as well as the boiled hay and left alone, the water will go green. With a little luck, daphnia will start growing or you can add some of your own.

As the infusoria starts the daphnia will eat them and multiply. You can cull them down for the fry and keep the culture going for weeks with added green water, fry powder and/or brewers yeast. If you have too many fleas at one time bag them and put in the freezer for later.

Adjust your water pH to between 7.8 and 8.4.


The spawning pond
Breeding usually starts around late September and into October ( southern hemisphere )and can run all the way to January. This all depends on the weather, the main pond temp and of course the *females*.

Around August you start preparation (cleaning) of the breeding pond and the hatching ponds, start preparation of green water and water fleas, clean and disinfect mops and breeding material. The spawning pond does not have to be large. I use a home made tank 1 mt wide by 2 mts long and 80 cm high, but you only have to fill to around 10cm above the back of the largest koi. By doing this you concentrate the eggs and sperm and have a larger hatch rate.

DO NOT feed the koi while they are in the breeding tank and make sure there is always plenty of oxygen. Fill your tank with treated, fresh water and if possible lower the water temp about 5 deg C below the main pond temperature. This will stimulate the females as it emulates the natural habitate. Their ancestors knew when to breed when they felt the temperature drop from the melting snow into the river.

String your mops and or breeding material along the length of the tank. Add your breeding pair in the morning and cover the tank (to stop them jumping out and protection from predators), check on them every morning as they will start to breed around first light. When they have done their duty they will start sucking on the eggs, the female will probably be very still on the bottom - exhausted.

Do not leave them in the breeding pond for more than 4 days. If they have not spawned in that time, take them out and try another pair.

Spawning materials
Spawning materials are used for the female to deposit her eggs at the same time as the male covers them with his milt. The material (mops) can be made from plastic bags cut length ways into strips and tied at one end and boiled to make them crinkle. Or you can make some out of nylon rope or use water hyacinth *as seen below*.

I use two lengths of nylon rope with plastic strips intertwined through the twists and tied off at each end of the tank at water level. I then place hyacinth between the two lengths of rope, this effectively holds the hyacinth in place. The rope & plastic mops last me 10 years and the hyacinth, a natural aphrodisiac for koi, has long, hair like roots for holding the eggs.

What ever you use make sure that you disinfect it before using.

Stages of spawning
This is the time that not only the breeding koi get excited but the novice as well, and maybe a little worried about their beloved koi being injured because of being chased and pushed around the pond. This is a normal breeding procedure.
Make sure that there is plenty of oxygen via air stones and that the pH is 7.
First the female sucks the breeding material while the male swims all around the pond so that he knows the limits and area that he can move in. When she is ready to lay her eggs, she swims in and through the spawning material. This excites the male and he begins to chase her. As they start to swim faster he pushes her towards the material with his nose, this builds into a frenzy of chasing and pushing the female over the material, butting her on the side for her to release her eggs. As soon as she starts to release the first spurt of eggs it gets really rough as the male can push her sideways and even lift her out of the water! Then they settle down to business, it is still a frenzy with the male all the time pushing her toward the material. As they get side by side against the material they, both in unison, flash their tails really fast, she releases her eggs and he covers them with his milt (blink and you will miss it).
This all starts very early in the morning just before dawn. A good indication that they have started is a strong smell and foam on the water. Approach them quietly as some koi will stop spawning if disturbed. Sit and watch for awhile and check them every hour to see if they have finished. This will be apparant with no activity and they have started to eat the eggs.
When they have finished remove them back to the main pond. The female will be exhausted but if she is a large koi and in condition, further chasing to empty her of eggs won't hurt her. When she has had enough she will just lay on the bottom an have no further interest.

Development of the embryo
Once the koi have been removed from the breeding pond leave the eggs to harden for 4 to 6 hours.

If you are going to move them to a hatching pond, DO NOT touch them or let them dry out. The eggs need to be disinfected against fungus spreading from the unfertilised dead eggs. This can be carried out in either one of two ways.

One way is to immerse them into treated, clean water for 15 mins. (treated with 15 P.P.M. of Malachite Green). Then the eggs can be moved into the hatching pond. Make sure that all the water is of a similar temperature to that of the breeding pond water.

The other way is to transfer the material to the hatching pond and treat that with 20 ml per 1000 lts of 1% stock solution Malachite Green or use the same as above at 15 P.P.M.

If you are using the breeding pond as a hatching pond, after the eggs have hardened off, carry out a 90% treated water change keeping the the temperature similar to which it was. Only fill to 30 cm high then disinfect the whole pond with eggs at 15 P.P.M. of Malachite Green.

Disinfection should be carried out only between the 1st and 3rd day after spawning NEVER after that.

The difference between infertile and fertile eggs is that the infertile ones are opaque and the good ones are transparent. Usually the infertile eggs are in clumps and start to grow fungus on them in the first few days.

Eggs hatch in around 4 to 6 days but this all depends on the temperature of the hatching pond. If it takes more than 10 days then I would say throw them away and start again with another pair as the deformity rate would be very high.

Care of the fry

Taking care of fry is very demanding and an important part of the breeding season but if carried out right it is very rewarding and makes it all worth while.

When the eggs hatch the fry are that small they look like a thread of cotton clinging to the sides, the bottom and the breeding material with their sucker. At this stage they have no mouth or fins, their gills are closed and they are living off their egg sacks. In a few days they will swim to the surface and fill their swim bladders and then they will be free swimming.

(One reason that you have at least a 4 year old female is the bigger the female the bigger the egg, and the bigger the egg sack for the fry to start on).

On day 4 after hatching remove the breeding material. The best will have hatched by now and by removing the rest which are mostly infertile eggs you will keep the ammonia level down.

The ammonia and pH levels are most important and must be kept in check (or you could loose the lot). Since there is no filter running yet and only air stones in the pond, Ammonia and pH must be monitored.

At between 5 and 7 days I treat the pond water and fry with CF 50 to reduce the risk of bacterial diseases and pathogens. At this stage the fry are feeding on infusoria and new born daphnia so no artificial food is required yet.

Now remember that you can not keep all the fry so thin them down to suit the size of your raising tank.

At around day 10 or when you can see the fry chasing and gulping down the daphnia its time to start feeding. There are many formulars but 1 I use at first:-

Boiled egg yoke and vegemite with a little fry powder in a 1lt of water. Mix in a blender and squirt over the pond.

The daphnia love the fry powder and vegemite but not too much at first, best to feed a little, 3 times a day.

After a week of this concoction I then go to fry powder. Sprinkle lightly over the surface 3 or 4 times a day plus a dash of yeast. Do not over feed as polution can kill them off. I also feed green water that I have been growing as well as daphnia. Always keep a check on the pH and Ammonia, if necessary do a 50% water change - but treat the new water.

Continue along these lines until they are about 3 cm long, then it's time to add a feeding dish and mix the fry powder and a little calcium powder into a past (not too wet). Roll small amounts into small balls no bigger than a small marble and drop them onto the feeding plate. If there is room, have more than one feeding plate around the pond. Feeding plates sit around 15 cm below the surface of the water.

In about a month after hatching if the fry are of a good size, it's time to start the filter BUT have a small pump not too much volume at first.


If you have come this far without losing the lot then congratulations, BUT now the real work begins. The fry should be around 6 weeks old and already you have culled out the bent and odd looking ones.

This is where you can lose the lot if you do not cull *severely*. As in nature, the parents only have to replace themselves so take this as a guide - nature will cull around 90% of the fry or more. One of the main problems is that hobbyists/ breeders try to keep too many fry and this is their downfall. You need all the room you can get to raise healthy, good quality fingerlings.

Culling hard goes hand-in-hand with good water and feeding practices. I cannot emphasise this enough, too much overcrowding leads to slow growth. This cannot be made up later and with cannibalism you could lose a winner. (If you over crowd, even your winners won't grow!)

Poor quality water = poor quality fingerlings.

Depending on the variety of fry, it may take 6 to 8 weeks before you can cull effectively as their colours and pattern have not fully shown through.

After the first culling it is time to add treated water so that the depth allows more room to move and for them to grow. I would not go over 60 cm yet but would have the filter running slowly.

You should re-cull every 8 weeks until they are 6 months old. By then you should have the best of them. If you have a problem with killing fry, then put the culls in a bag of water and put in the freezer or have a bucket handy with MS 222 in it to anaesthetise them. For me, after so long doing this I just bury them in the garden, they make very good fertliser for my tomatoes!

When they are about 6 months old you should have enough to choose the best tategoi (young koi with potential) and thus reducing your numbers again.

Do not put the young koi in the main pond yet as the larger koi give off an enzime which will stop the growth of the young tategoi. When they are at either 9 months or 20 cm then it will be safe to put them together.

Tips on culling
This can be a daunting task for the novice but this is how I cull:-

Choose a good sunny day do not feed the fry before culling. Pick a spot in the shade close to the pond have ready: tubs, air stones, buckets, nets, table and stool if required.

I have a floating timber box with fly mesh on the bottom which is about 1/2 mt square and 15 cm high. This floats in the pond and I use it to hold around 100 fry I have caught in a large net. I then transfer about 20 fry to a tub (with pond water and an air stone in it), from this tub I pick out the culls and dispose of them into another bucket. The good fry are then transferred to another tub filled with pond water and air stones. Keep in mind to not over heat the water as stress is a killer, I advise changing the water regularly.

I continue this method until I have finished the whole pond. Only around 1/3 of these could be worth keeping after the next cull. When the pond is empty I transfer the good ones back into the pond and go on to the next pond.

~ The first cull is to take out the deformed ones and the solid colours (if your spawn is Sankes, Showas etc).
~ As you progress along to the next culling sessions you look for pattern and colour all the time raising the standard of acceptance untill finally you have up to 20 good fry to raise to a bigger size.


H. Watson