Breeding Koi and Goldfish

Koi Goldfish Hybrid

Guide to Understanding and Successfully Breeding Koi & Goldfish

koi goldfish hybrid

We are going to submerge ourselves into a MIND-BLOWING article as we dig into breeding koi and goldfish.

In the goldfish world, it can’t get any more intriguing than this!

Your average fish pond that graces landscapes are full of what most perceive to be koi or goldfish.

Little do they know that if both types of fish are in the pond, there will most likely be a population of hybrid fish among them.

Before we dive into breeding koi and goldfish, it helps to understand more about the two.

Are koi and goldfish the same thing?

We are excited to answer this question with a plausible, “NO!” 

Although they look alike with features but have different body sizes, they are not the same kind of fish.

They both originated from the carp family, but the TYPE of carp they came from is what sets them apart. 

Let’s take a look at what sets these two fish apart!

breeding koi and goldfish

The Differences in Koi and Goldfish

Koi Fish

Originated from: Common carp

Physical Characteristics:

Size 36”

Distinguishing Features

  • 2 sets of barbels (whiskers) near mouth
  • More variation of colors
  • Colors are vibrant

Body Shape

  • One common shape

  • Rounded nose

  • Slim-elliptical body

Cost: $25 - $1.8 million!

Lifespan: 25-35 years



  • Fish to water ratio: 4” per 100 gallons
  • Requires big body of water with minimum depth of 36”

  • Eats more food than goldfish resulting in more fish waste
  • Bottom rummager (barbels on lips help to forage and find food)

Spawning: Once a year

Behavior: Friendly but will eat small things such as smaller fish.


Originated from: Prussian carp

Physical Characteristics:

Size 6-10”

Distinguishing Features

  • Less variation of colors
  • Color vibrancy limited to certain varieties

Body Shape

  • Egg-shaped and Streamline-bodied

  • Blunt nose

  • Rounder body

Cost: $5-$50

Lifespan: 5-10 years



  • Fish to water ratio: 1” per 10 gallons
  • Lives in tank environment or small pond

  • Eats very small portions compared to koi resulting in less fish waste
  • Feeds mainly at surface or middle of tank

Spawning: Twice a year

Behavior: Friendly

The most expensive koi in the world brought a whopping $1.8 million dollars! 

What does Koi-Goldfish offspring look like?

The offspring of koi and goldfish have interesting features. There are characteristics to look for when trying to identify a koi-goldfish hybrid.
  • Barbels: One small pair or none at all
  • Scales: Noticeably more lateral line scaling
  • Size: Somewhere in between the size of a koi and goldfish
  • Peduncle: Caudal peduncle is thicker than a goldfish
  • Sterile: Unable to reproduce
  • Fins: Rounder than a goldfish
  • Tail: Has the appearance of a single-tail goldfish

Breeding Koi and Goldfish

koi fish breeding

Warm pond water encourages spawning.

Unless you are monitoring your pond continually, you may not be aware when spawning occurs.

A significant indicator of spawning is a foam-like film on the surface of your pond water. You may also notice a strong fishy smell. 

So, you are interested in breeding koi and goldfish? 

Let’s take a look-see on an easy DIY breeding setup and system.

Easy DIY Koi-Goldfish Breeding 

The key to successfully breeding koi and goldfish is to get to the eggs before one of them devours them.

The spawning season generally occurs when the water temperature spikes during the summer.

Plan ahead and have everything in place before your fish spawns. 


1. Set up a Separate Pool for the Eggs

  • You can use a small swimming pool, stock tank, IBC container, old bathtub, etc.

  • Install a filter system.

  • Cover your pool to prevent birds from eating your daphnia as well as dragonflies and other insects from laying eggs.

  • Fill with water and allow it to sit for a few weeks until algae has formed.

  • Add daphnia (live) to water. Daphnia are basically water fleas. They will provide an endless source of food for your fry after they hatch.

    • You will need to feed the daphnia every 4 days from this point forward. 

      Sprinkling active dry yeast over the surface of the water will keep your daphnia fed and happy. 

      Daphnia reproduces at an exponential rate, so you never have to worry about restocking.

2. Place either a spawning mop or egg media in your fish pond to catch the eggs.

Wait and Watch

koi fish pond

There is a tale-tell indication that your fish have spawned.

A foam-like film covers the water, and a strong fishy smell may be present.

If you notice this, it’s time to check the pond for eggs.

Transfer the Eggs

  • Transfer the eggs to your pool. 
  • The eggs will hatch 5-7 days after they have been laid.

Caring for the Fry

  • Ensure that your pool cover stays on. Birds will feast on your fry if not covered.
  • Routinely test your water parameters. Pay attention to the nitrite and nitrate levels.
  • If you want to add pellets to their diet, you can feed them small pellets once a day.
  • Your fry will need to remain in the pool for at least 1 month or until they reach 3” before they can be transferred to the pond. Some experts recommend that you keep fry separate from adults for up to a year.

And there you have it!

beautiful koi fish

If you have a koi pond stocked with goldfish and koi, you now have a fairly simple way to breed them.

To be successful, you have to scoop up the eggs before they become dinner for mom or dad in the pond.

If you can do that and transfer them to the pool in time, you will have an awesome time watching the process of fish hatching to growing up.

Good luck and we hope you have many fry in your near future!