Breeding Koi

 In This Chapter

• Knowing the highs and lows of breeding koi
• Expecting the unexpected in breeding
• Preparing the koi and their breeding site
• Making baby koi — thousands of them
• Staging the hatching grounds
• Natural breeding: Baby koi made simple

What if you want to get in on the ground floor, so to speak, when it comes to good koi? Breeding your fish and watching as the fry (hatchlings) emerge from the eggs is a real highlight of koi-keeping.

Breeding koi can be a complicated but fulfilling hobby. It certainly opens up a new world of knowledge, pond maintenance refinements, and koi behavior, and it offers you a ringside introduction to koi-keepers who regularly and successfully produce koi.

This chapter helps you decide whether you’d like to start a breeding program and what’s involved if you do. We also give you a heads-up on the characteristics you can and can’t breed for.

To Breed or Not to Breed: That Is the Question

Do you really want to breed your koi? Watching your fish reproduce can open up a whole new aspect of the hobby to you and will likely hook you on koi for good. You learn a great deal in the process and may even be able to add your own unique twists that can help future koi breeders.

Consider some of these pros for breeding:

- It’s a do-it-yourself way to get more koi. At the same time, you have the fun of watching the young grow and see how their colors develop over time. (Let’s see, this is year five, so the red [called Hi in koi terms] should be getting deeper and the Sumi should be spreading. . . .)

- You can make some cold, hard cash. Other koi-keepers like and appreciate koi, and most of them like to add to their collection. Of course, this is only a benefit for those who have a market (that is, can sell their koi) and can make enough money to at least break even.

- The learning process is very stimulating and will probably spur you on to read, research, and speak with other hobbyists and professionals.

- The lessons you pick up from breeding koi are transferable to other fish species if you’re inclined to expand your interests. _ Breeding is a great way to attract friends and family to your hobby and to share it with them.

Breeding also has some negative points:

- It takes time.

- It takes money.

- It takes additional space.

- It’s a boisterous sport; your fish, especially your female, may be damaged (see “Letting your koi have at it” later in this chapter).

- Most noticeably, it can produce tens of thousands of baby koi. Many die off before you make a single move toward culling (selective reduction), but you still need to cull, probably several times (see Chapter The Small Fry: Bringing Up Baby Koi for more on this process). At the least, you end up with a hundred or so 1- to 2-inch baby koi.

Predictions You Can Make (And Those You Can’t)

Trying to predict what characteristics will be expressed (that is, be evident) in a particular breeding is complicated, mostly because we don’t know what recessive genes a given koi carries. As a result, breeding between a selected pair of koi produces a hodge-podge of gene expression in the 5,000-plus young.

Remember

If you were to keep records and photos from breeding the same pair year after year, maybe you could get a sense about the young koi from that pair — but maybe not. Breeding koi is that unpredictable. You can only be sure of two facts: They’ll all be koi, and only some of them will look like one parent or the other — many won’t look like either.

Nevertheless, some characteristics in koi do breed true. Take a look at the following characteristics to get an idea:

- Scale patterns: Normal-scaled koi that mate with each other generally produce normal-scaled offspring, and mated pairs of mirror-scaled koi usually produce mirror-scaled young. Parents of both types, however, can carry the genes for other scale patterns, in which case the fry’s scales will vary.

Leather-skinned koi pairs produce leather-skinned (predominantly) and mirror-scaled young.

When line-scaled koi are paired with line-scaled mates, the resulting young exhibit a variety of scale patterns.

- Metallic sheen: Metallic sheen is dominant over normal sheen when the parent koi are a white-skinned or black-skinned variety. If both parents have one gene for metallic sheen and one for normal sheen, they and their offspring look metallic.

- Color and color pattern: Koi color genetics are complex, and two koi that seem identical in color and basic pattern may arrive at that color and pattern with differing genetic mixes.

Unless you begin with a male and a female of one variety from a single lineage (like two closely related koi from a dealer who specializes in that variety), the patterns of the offspring are impossible to predict. So you can breed for a red and white Kohaku; you just can’t breed for a heart-maruten on the head or for zigzag placement of the red along the body.

Remember

Pattern, alas, doesn’t pass down from parent to offspring. You can’t tell what colors are going to pop out until you have the growing fry in front of you. So what do you do? Start with strong, well-shaped, and well-colored adults of the same variety and hope for some surprises — which, given 5,000 variations, you’re apt to get.

Don’t let the unpredictability aspect throw you. It’s part of the fun of breeding koi. The market for a breeder’s affordable, handsome koi is much larger than the market for expensive offspring of Nishikigoi.

Preparing for the Dirty Deed

Koi are prolific breeders and are, as a species, well adjusted to captive life. This does not mean, however, that you can simply put two fish of opposite sex together, sit back, and wait for babies. (Although sometimes — especially in large, outdoor ponds — this is exactly what seems to happen.) If you (and your koi!) are to be successful, you need to plan carefully. Be sure that you have the time, patience, and space for this complex but rewarding endeavor.

The season for breeding usually begins in February and continues until May, depending on when the water temperature reaches 68 degrees F and when the fish (including the male) become more active and begin to feed. Because exact breeding times vary from place to place, season to season, and even among individual fish, have your breeding tank up and running at least two weeks before the earliest possible beginning of the local breeding season.

Formal breeding operations know how to eliminate as many of the variables as possible. But even as a newbie, you can minimize your challenges by making sure

• Your koi are as healthy as possible
• The breeding site is easy to monitor
• You use an easy method for changing the water
• You have enough room to move the adult koi in and out as necessary

Gathering the necessary tools

To help your koi successfully enter their parenting stage, some advance setup is necessary on your part. This section walks you through the details of the tanks and their essentials to make the breeding process as predictable and smooth as possible.

Selecting the breeding tank or pond

Most koi breeders set up one or more breeding ponds indoors or outdoors, depending on the springtime temperatures and the available space. Because the breeding tank often becomes a nursery after breeding (see “Setting up the nursery tank” in the next section), indoor tanks or ponds tend to be easier.

Polyethylene stock watering tanks or show tanks make good breeding tanks for koi. (Stock tanks are available from livestock/farm supply stores, and show tanks are sold in pet stores or pond supply stores.) Look for one that’s about 200 gallons. This size (at least 4 x 4 x 2 feet) provides enough room for the female for a month or two before fertilization, then the female, male, and spawning brushes (for the less-than-12 hours for egg deposition and fertilization), and then the 2,000-plus fry.

Selecting the hospital tank

A second tank serves as a hospital for the female so she can rest up for a week or two after laying her eggs. A stock watering tank or show tank of at least 200 gallons will suffice. See Chapter Keeping Koi Inside for details concerning this enclosure.

Supplies needed for each tank

Now that you have the tanks, they’ll need to function just like your pond. So each tank needs its own

- Water pump

- Filter

- Air pump

- Airstones: Airstones connect to the pump and are made of a porous material. They diffuse air from the pump so it rises to the surface as a fine mist of bubbles. These bubbles disturb the water’s surface and cause oxygen to be mixed into the water.

- Heater

- Net covering

- Spawning brushes: Spawning brushes are meant to imitate plants, the usual spawning site for koi.

You can also use slender, smooth, tree branches (willows are a good, pliable choice) that you tie together at their ends and place into the tank. (If you use live branches, first wash them in soapy water, then rinse them, dip them into a solution of 10 percent bleach, and re-rinse to remove traces of insecticides and pollutants.)

Chapter Keeping Koi Inside has more info on these supplies. Note: When you total them up, the supplies can get a little pricey. Consider checking out Amazon.com for used supplies to save on your setup investment.

Getting the breeding grounds ready for showtime

Before the weather warms, you need to prepare for the coming breeding season. As we mention earlier in this chapter, the onset of the fish’s interest in reproduction is subject to many variables.

Your best guides are local koi-keepers who’ve been successful in breeding their fish.

Setting up the breeding tank

Reduce the water in the tank to expose about a foot of the tank sides; add airstones to agitate the water.

Place the spawning brushes in the water (they can float freely), and introduce the female. She’ll likely nose about the tank for a while as she explores this new environment.

Setting up the nursery tank

The nursery (or incubator) tank should be up and running by the time the adults are ready for breeding. Keep it filled to about 6 inches below the lip so the fry can’t jump out.

Add filtration and airstones. If you locate the nursery tank outdoors, you can simply put it online with the same filtration system as your koi pond. This step assures that the tanks are the same pH and temperature. Use an air pump to power up the airstones. As an alternative, you can use the breeding tank as a nursery tank.

Casting the stars of the show

In the excitement of your first breeding success, don’t neglect to plan for the future. Although you can’t imagine forgetting even one aspect of the event, be assured that time will blur the details. Keeping accurate records allows you to analyze and refine your methods in the future and can add to your overall understanding of this adventure.

Remember

Keep breeding records on your koi, even if the offspring seem only slightly better than average. Anyone who obtains one of your offspring and decides to breed his own koi will appreciate a copy of the lineage, if only to get an idea of possible dominant and recessive genes.

Tip

In all cases, keep photos with each record unless you have only a few, easily identified adults (in which case you can describe each accurately). By taking photos every six months (and labeling them!), you can easily provide a record of your koi’s color development.

Telling the sexes apart

Adult koi are fairly easy to sex from the body shape alone. The females are plumper than the males, who look rather streamlined in comparison. Adult females also have smaller pectoral fins. But for younger koi, you have to rely on more subtle clues.

When breeding season starts in spring to early summer, the males (even as small as 5 or 6 inches long) develop a pebbly forward edge on their pectoral fins. The forward edge of a small female’s pectoral fin is smooth. Although you can feel the difference with your finger, we’ve heard of koi fanciers whose sense of touch has dimmed, so they use their tongue to feel the pectoral fins. (Trust us; you don’t have to do this.)

Females also tend to have larger, rounder pectoral fins than the males. (See Figure 14-1 for a visual of the differences between the sexes.)

Choosing the optimal fish

For breeding purposes, select adults on the basis of color, body shape, finnage, and scales. Fish are judged from above (no, not that kind of Above — from the tops of their bodies), so select koi that are prettiest from the top.

- Number of each sex: You can use just one or more males per female. (We talk about a single male in these instructions so you know what the young from a particular pairing will look like.) Many breeders use two or three males per female on the theory that competition makes the breeding more intense.

- Age: Select females that are 3 years old or older, although particularly robust females may successfully breed at age 2 or so. Males should be at least 2 years old, preferably 3, and they have no upper age limit for breeding.

• Females need to be healthy and fully mature to endure the rigors of egg laying and to produce vigorous young. If you have any concerns in this regard, wait until your koi is 4 years old before pairing her with a male.

Because breeding takes more out of a female, the oldest practical age for a female breeder is 5 to 8 years.

• Males that are 3 years old or older are better able to joust with other males during breeding and not get damaged. They’re also stronger than a smaller koi and better able to position themselves over the eggs to fertilize them.

One breeder uses a male estimated to be 20 years old because he throws great babies.

- Size: Larger females can better tolerate the battering process involved with spawning, and they can produce more eggs. Although your first response may be, “Who in the world needs more than 50,000 fertilized eggs?” these eggs are also larger than those produced by a smaller female.

Larger eggs have larger yolks, which means larger fry and more nourishment for the fry in the first days after hatching. In addition, bigger fry can switch to a commercial diet earlier than small fry, which means they grow faster than the fry that must live off their yolk longer.

Grooming your koi for the rendezvous

Koi breeding is triggered by the lengthening photoperiod (the longer days in spring) and the warmer water temperatures (70 degrees is a good marker). Note: The Japanese believe that a full moon triggers egg laying, which may give you an indication of when to expect spawning.

Frequently breeders take the chosen female out of the pond in January and place her in the breeding tank to begin feeding and building up body weight.

Figure 14-1: The difference between a male koi (a) and a female koi (b). 

Remember

If your tank is indoors, be sure the room has a natural photoperiod. You can add timers to the lights to mimic normal, increasing day lengths; this trick helps nudge the female toward breeding readiness.

The male you’ve selected can stay outside in the pond (like a cold shower, only different) until the weather warms a bit.

Getting Down to Business

As is true for most fishes, koi engage in specific, if sometimes subtle, behaviors that signal their readiness to breed. If you want to recognize these and plan appropriately, you need to tune into your koi’s normal behaviors. By carefully observing your fish over time, you can easily note changes that may indicate the onset of breeding behavior.

Beginning the breeding

Your first clue that egg laying is imminent is when the female begins to nose around the spawning mat and any other possible egg-deposition sites. She will be followed by the attentive and eager male(s), who is willing to do his part and fertilize any eggs the female may wish to deposit. At this point you can move the female to the breeding tank.

About sunset of the same day, place the male in the tank with the female, making sure to stretch the netting over the top of the tank.

Allow the fish to stay together through the night. The entire process should take about four hours. Eggs are usually laid in the morning, just before sunrise.

Tip

Stay in the same room for a time in case the male gets too aggressive toward the female, in which case you can remove him and substitute another male. Please note that this is a difficult call — especially for a novice — because normal mating behavior can seem pretty rough to the uninitiated. If at all possible, join a local koi club and try to observe breeding at a member’s pond so you know what to expect. The male’s presence may inspire the female to spend more time exploring the spawning brushes. This is normal behavior and requires no action on your part.

Letting your koi have at it

As the time of actual egg laying approaches, your koi exhibit a series of behaviors designed to synchronize the activities of both parents. Because fertilization is external, both male and female need to be in the same frame of mind if breeding is to be successful.

1. As she prepares to release her eggs, the female releases a signal pheromone (the sexy scent) that excites the male.

2. He then wrestles with the female, head-butting her, nipping her, and shoving her with his body as he pushes her toward the spawning brushes.

Her fins may be damaged in the process and she may lose scales or even flesh to the male’s bites. The netting you use to cover the tank prevents both koi from leaping or being shoved out of the tank.

3. Encouraged by the head-butts from the male, the female spews eggs from her vent.

The eggs are coated with a sticky mucous so they stick to the brushes and sides of the tank.

4. The male, further signaled by the pheromone, releases his sperm (also called milt).

The milt, which looks like a milky haze in the water, is wafted by water currents over the eggs. The sperm enters each egg through a small pore called a micropyle. After fertilization, the micropyle closes.

5. After she lays the first batch of eggs, the female pauses and snacks on a few eggs. The male does the same.

Then the female lays more eggs, the male nudging her as she does so, and he releases more sperm. They pause to snack on eggs, she lays more eggs, the male jostles her and fertilizes the eggs, then they pause to snack . . . and so on until she has released her entire supply.

The faster the eggs are laid, the faster they can be fertilized and the male can leave to become less obvious. Even when all the female’s eggs have been laid, the male continues to butt her in an exploratory way.

6. When she’s too tired to respond, he turns and begins eating the eggs. At this point, you can remove him so he can start handing out cigars to the guys in the pond.

Reaping Your Reward: Parenting the Eggs Till They Hatch

Egg laying is an important milestone, but this is no time for you to sit back and relax. The care you give to the adults and the eggs from this point on greatly influences the future of the clutch.

In the beginning . . .

This is a busy time for the eggs and for you, the proud, new breeder. Do the following on Day 1:

1. Make sure the filter is working in the nursery tank and double-check your water:

• Chemistry levels must be within acceptable limits.
• The water temperature should be about the same temperature in the breeding and nursery tanks.

2. When the female has finished laying, lift the spawning mats in a net and move them into your nursery tank.

(You’re probably going to see lots of eggs; females generally lay from 20,000 to 50,000.) As an alternative, leave the eggs in the breeding tank and simply remove the adults.

3. Move the female to the hospital tank (see “Selecting the hospital tank” earlier in this chapter). As always, take great care in transporting both the male and female.

4. Check the ammonia level in the nursery tank shortly after adding the eggs.

The protein from the eggs and the sperm may cause the ammonia level to jump.

5. If the ammonia readings merit it (ideally, you’re aiming for a reading of zero), do a very slow partial water change (20 to 30 percent over an hour), or use a product like AmQuel Plus to reduce the ammonia levels.

At this point the breeding tank water has a slight color or cast to it and a slight but distinct smell.

6. Slowly add water from your pond at the top and siphon out water from the bottom.

Keep the flow rates equal so the water level doesn’t drop and expose any of the eggs to air.

The water change helps with the odor problem, and the odor will dissipate over time.

7. Position the airstones to create a gentle current in the tank by distributing the stones evenly in the tank. The water filter should be off.

8. Sit back for a minute and admire the tank.

The eggs are scattered on the sides and bottom and on the spawning brushes and are quite visible, looking a little like pearl tapioca. In about two weeks, you’re going to have a bunch of baby koi (and less time to sit!).

Because you aren’t feeding any fish yet, the water quality should remain stable. A fine growth of green algae in the bin is a reason for joy, not despair, because the algae and the microscopic protozoans it harbors will be eaten by the tiny fry.

Moving on up

The first home for your hatchling koi will be the breeding tank or bin where they were conceived. This section walks you through your first six days as a koi breeder — when your progeny transition from fertilized egg to showing their first signs of life.

In a day or two, the eggs that aren’t fertile turn white (and then develop a fuzzy fungus coat). The fertile eggs are clear except for two very small dots per egg, which are the eyes of the soon-to-hatch koi.

For the next few days:

• Keep the airstones fizzing.
• Siphon out or net out the unfertilized eggs.

Six days later, hocus-pocus: A lot of tiny, 1⁄4-inch-long fry are jiggling about in the nursery. They have a bit of residual yolk, so they don’t need feeding this first day.

If you have a high hatch rate and you’re overwhelmed by the sheer numbers of fry pulsing through the tank, make your first cull (see Chapter The Small Fry: Bringing Up Baby Koi) with these steps:

1. Make a couple of passes through the fry with a fine fish net.

2. Discard the fry inside the net.

Tip

Cover the bin or tank containing your new fish with bird netting if there’s any chance of bird predation on your young koi. As small as they are and as many as there are, a heron or egret may find a sampling worthwhile.

When the fish get to be 1 inch or longer, your neighborhood raccoons may stop by one evening. Raccoons are quite resourceful animals and are not thwarted by bird netting. If you expect to run into trouble with raccoons, keep your young koi in a container that can be fitted with a tightly locked cover.

Low-Maintenance Breeding: The All-Natural Love Pond

You don’t have to go full-tilt to breed your koi; the second way is to let nature take its course (either by simply leaving your koi to their own devices or by furnishing a habitat that’s suitable for baby koi making).

If you let nature take its course, be prepared to accept a tremendous attrition rate because of egg predation by adults and the spread of fungus from infertile to fertile eggs. Naturally, the outcomes of such breedings vary widely from pond to pond and season to season. One koi-keeper we know has only three or four new young koi in her pond every year as a result of leaving the adults to their own devices.

Sectioning off the in-pond romping grounds

If letting your koi enjoy free love just isn’t your thing, but you don’t want to hassle with the breeding tanks and such, you can section off part of your pond and create a nursery there. This nursery serves to confine the breeding adults to one area of the pond for a time so the eggs are in one location and therefore easily relocated. To create a nursery, follow these steps:

1. Start by digging out that seine net you used last year to round up your koi for their winter pond and the spawning brushes you bought at the koi conference you attended.

2. Use the seine to confine the female and one or maybe two males to one end of the pond, and add the spawning brushes to that end of the pond.

3. Turn off the filter and the foam fractionator for a couple of hours.

This step helps the eggs stick to the spawning brushes instead of floating out of the spawning end of the pond.

4. After courtship and spawning ends, use a net to move the egg-laden brushes to your nursery tank. Turn the pond filter back on, and return the male(s) to the main part of the pond after a few hours.

Warning!

By turning on the filter and the fractionator before you put the breeding male back into the main part of the pond, you avoid problems. The other male koi, invigorated by the scent of the female’s pheromones in the water and on the male, get confused. They pummel the newly returned male to try to get him to release eggs. If the filtration systems run for an hour or so before you release the breeding males, most of the scent dissipates or is filtered out.

5. Leave the female by herself in the spawning end for a few days or move her to a hospital tank with very high water quality for half a day or a full day. See “Selecting the hospital tank” earlier in this chapter for more about this tank.

This break lets her rest from egg laying and the enthusiastic attention of the males.

Preparing your pond for babies

Can you have a pond that’s breeding- and baby-koi-friendly without a lot of extra equipment and effort? In a word, yes. You can make a few accommodations to help ensure the survival of some fry. They simply need food and shelter, so you need to provide a substrate (site) for egg deposition and hiding spots for the koi after they hatch.

To provide egg-deposition sites and shelter for the fry, position spawning brushes or mats or slender tree branches on the floor of the pond. Tie either device to a line that extends over the pond edge and anchor it to a brick or a rock. The line allows for easy retrieval after the young are large enough to fend for themselves.

The tiny koi don’t need much space, but they’re vulnerable to predation. Adult koi and such unwelcome visitors as predacious aquatic insects relish tiny fry, and raccoons and wading birds will consume those that survive and grow larger.

Tip

To provide a hiding area for the baby koi, plant ornamental grasses or pond-side plants that overhang the edge of the pond. If the pond has no place near the edge for living plants, tie leafy plastic plants together and hang them at the pond’s edge with a line that’s anchored by a rock. If the pond’s edge is tiled, try looping the line around small suction cups stuck to the tile.

by R.D.Bartlett and Patricia Bartlett