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How can I tell if I have male or female koi? | Decorative Ponds & Water Gardens Q & A

Q: How can I tell if I have male or female koi?

Q: How can I tell if I have male or female koi?

Ann Marie – Casselberry, FL

A: If only koi were as easy to sex as a pair of peacocks! Like those fanciful birds, koi are sexually dimorphic – meaning the males and females look and behave differently – but it’s not an easy distinction to discern. They grow to roughly the same size and they both have colorful scales, yet there are subtle differences if you know where to look. With these clues, you’ll know whether to name your finned friends Fred or Frieda.

Clue #1: Age

Koi are easier to tell apart when they’re mature, and so your first clue will be age – which is related to their length. They’re considered mature (3 years old) when they’re about 10 inches long. If they’re between 3 and 10 inches, they’re still juveniles and may be difficult to sex.

Clue #2: Body Shape

Immobilize your koi by capturing it in your Collapsible Fish Net and take a look at it from above. A mature male koi will have a slender looking body, while a female koi will have a rounded body, particularly when it’s spawning season and she’s carrying a nest full of eggs!

Clue #3: Fin Shape

Next, examine your koi’s fins. A male koi’s pectoral fins, the ones near his head, will appear pointed and solid in color. In addition, the first ray of his pectoral fin may be more substantial when compared to his female counterpart, which will display rounder fins.

Clue #4: Tubercles

During breeding season, you may see little white growths, called tubercles, on male koi’s heads and pectoral fins. They’re perfectly natural and will disappear once the fish have finished getting frisky. Females don’t develop these protrusions.

Clue #5: Behavior

One final – and obvious! – clue: amorous behavior. When they’re not mating, they behave very similarly, but during mating season, the male koi will chase the female, encouraging her (sometimes enthusiastically) to release her eggs so he can fertilize them. After all that frolicking, the happy pair will benefit from some Pond Logic® Stress Reducer Plus, which will help heal any damaged tissue.

It’s not easy to distinguish the male and female koi, but with these tips and clues, you’ll know your Freds from your Friedas in no time!

Pond Talk: Have you ever tried to determine the sex of your koi?

Safely Catch Your Fish - The Pond Guy® Collapsible Fish Net

Why are my koi chasing each other? – Decorative Ponds & Water Gardens Q & A

Why are my koi chasing each other?

Why are my koi chasing each other? Christie – Moline, IL

The Thrill of the Chase

Just like any other pet, Koi provide pond guys and gals everywhere with entertainment and companionship. So now your new found finned friends are chasing each other around and being rather aggressive towards each other. This violent activity may seem disturbing to us but for your Koi it is actually a natural process. No your fish have not transformed your water garden in their very own fight club; this is their way of courting each other.

With Friends Like You…

So nothing says love like bashing your partner into a few plants and rocks right? What you are seeing is the male Koi(s) chasing the female around the pond trying to push the eggs out of her by pinching her between rocks or other males. It is during this process that the eggs are released into the water and fertilized. While we may have been a little slow to realize love is in the air … or in your pond rather, there are still a few things you can do to help your Koi have a successful spawning season.

Bring On The Plants: Adding Aquatic Plants like Hornwort and Water Hyacinth in your pond will provide excellent surface area for freshly laid eggs to attach to and will also provide coverage for them.

Keep It Clean: It is important that you keep the water in your pond clean and free from disease while the fry are developing. Perform regular water changes and use Water Conditioner when adding new water to remove any chlorine and toxic heavy metals from your tap or well water. Make sure you are adding Pond Salt to the water to keep fish stress down and also help prevent diseases.

Survival of the fittest…

After the fry hatch, you may not see the new additions until they become big enough to fend for themselves. Once they hatch they hide and fight for survival. Koi are not loving parents, they tend to eat their own eggs and fry. Out of thousands of eggs koi lay, only a select few will survive.

As your new additions began to grow, there will be added ammonia and nitrates in the pond. If you plan to keep these new Koi make sure you are providing adequate Filtration in your pond and you are not deviating from a practical fish load for your size pond. Having more fish in your pond than your filtration can handle will lead to additional more severe algae blooms and muck accumulation. It is important that you keep adding beneficial bacteria such as Nature’s Defense® or Muck Defense® to break this waste down.

Pond Talk: Have you seen baby koi in your water garden?

Pond Logic® Pond Salt

Why is One of My Koi Is Bumping Into Another? – Water Garden Q & A

Picture of One Koi Bumping Another

Q: I have koi in my pond and one of them is constantly chasing the other fish by bumping and nuzzling the other fish on their bottom side in front of the tail and behind the ventral fin. Is there a reason for this behavior?

A: Yes there is a reason for this. The fish getting bumped into is a female carrying eggs, while the fish doing the bumping is the male. The male fish is trying to knock the eggs out of the female so it can fertilize them. This is very common, but it is best to keep an eye on the fish during these times to make sure no injuries happen. Also, if you would like the koi to have babies, I would suggest making sure you have a sufficient amount of bog and submerged plants. Koi are known to eat their own young and adding aquatic plants will create hiding spaces for the babies to allow them time to grow.

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