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Can Koi and Goldfish Breed? – Decorative Ponds & Water Gardens Q & A

Can Koi and Goldfish Breed?

Can Koi and Goldfish Breed? Sheldon – Huntington, KY

Would That Make It A Koldfish?

Your fish have finally spawned and after what seems like eons of waiting they are starting to grow into full grown Koi…or Goldfish…or…what are they? Your newcomers seem to have unique new patterns and colors that are difference than their alleged parents, is it possible your Koi and Goldfish have crossbred?

While it is possible to crossbreed the two types of fish, it is fairly uncommon for the process to naturally occur in your pond. The outcome of such instances yields sterile offspring that are unable to reproduce. It is much more common to produce new colors and varieties of fish due to two different types of goldfish reproducing. While some pond owners are curious about the potential to crossbreed their fish, many more would be happy to just experience the spawning process even once in their back yard water garden regardless of the results. If it has not happened for you yet, make sure you are providing adequate habitat in the form of submerged plants so if your Koi do spawn the eggs and fry will have places to attach and hide to avoid becoming an easy meal (yes Koi will eat their own young). Furthermore, maintain a healthy water feature by providing adequate filtration, aeration, and beneficial bacteria. Using the products in a Pond Logic® DefensePAC® will give you a wide assortment of products that simplify your pond maintenance and promote a clean healthy environment. Click over to our Koi Spawning Blog for a little more insight on the matter.

Pond Talk: Have you ever experienced this phenomenon?

Water Hyacinth

23 Responses

  1. I am new to having a pond. I purchased 2 Koi fish in April 2017 (about 2 inches in length) I don’t know if they are male or female, along with the koi I have 5 different types of gold fish. Now its August 2017 (Koi/s are 8 inches long) and I have like 30 little fish in my pond. Some are greyish and look like gold fish the others look like baby Koi and have a mixture of colors. I thought Koi fish would not breed until they are mature ( 1 -2 years old).

    • Hi Aida – This can sometimes be tricky, eventhough the koi may have been on the smaller side they may have already been close to a year old by the time you got them. Since koi and goldfish or even just different species of goldfish can breed together you most likely won’t know for sure if the babies are goldfish, koi or a mixture until they are much larger. For now just enjoy the extra company!

      • Thanks for the reply, I must say I enjoy my fish. I have like 100 little fish all sizes they must love to breed. My pond is only 600 gallons hopefully they will be ok in a pond that size. Thanks again

    • Aida: Several years ago I had 1 Sarrasa Comet along with 3 Koi. When I eventually saw “babies” in the pond, I wondered who bred since I couldn’t identify the babies because they were too small, and most were dark grey. By the following spring, some developed spotting which looked like Koi; others remained grey except for a slight hint of metallic orange on their undersides. I eventually traded in all but the one that stayed dark grey. I read that black Koi are considered good luck, so I kept him. As he grew, he remained that color and had the shape of a Comet, no “whiskers”, so I then knew that the Comet mated with one of my Koi. The parent Comet is no longer, but the baby I kept (and still have) is named Darth Vader. He may not be my good luck black Koi, but he’s special nonetheless!

      • Thanks for the reply. I really enjoy watching my fish. Since this post I realize I have over 100 little fish. Some are white with orange spots, some are gold and some are grey. I might be to many for my pond but I cant seam to catch them to give them away. Maybe by next spring they will be bigger and easier to catch. I believe I also have 1 Sarras Comet ( I looked it up and I looks like one) But they are beautiful. Thanks again.

  2. I have a garden pond Koi Schubinks and comets. Now have a number of dark fish that look like minnows. Is that possible?

    • Hi James – Koi are very tiny when first born and you may not even notice them in the pond until they get to be the size of a minnow. Colors can also range from dark to orange and everything in between. Watch them closely as they will most likely change in color as they continue to grow.

  3. I just had an interesting experience that seems to be on topic here.
    I’ve been tending to a 1200 gallon pond for 15 years. Originally had 8 koi that reproduced for several years and probably increased to @ 30 total. Unfortunately due to filter/pump malfunction, herons and some afflictions lost all but 1 large koi.

    Fast forward a few years. Last year, added a comet and shebunkin being told by my local vendor that they would not breed with koi. These new fish are very timid and I believe that only one of them survived (comet?).

    Over past 2 days, noticed koi being VERY animated. Today, water hyacynths & side of pond loaded withe tiny white eggs. It will be interesting to see what develops, but I hope I don’t have a major population explosion upcoming.

  4. I guess this must sound crazy but is there any to slow down my fish reproducing? I have 3 koi and several adult goldfish that got upgraded from a 400 gallon to 1800 gallon pond in December. In the past 6 weeks I have seen at least four new sets of fry; the oldest are about 1.5″ long already. My pond is getting overpopulated fast. Any suggestions other than bringing in a bluegill? I’ve got over 3 dozen young fish that I know of. Anyone in central akabama…. Come and get them please!!!

    • Hi Scarlett,

      Unfortunetly I don’t have to many other options other then finding a friend to share with. While it may seem like you pond is getting out of control at the moment take pride in the fact that you are providing a well balanced and happy environment that’s encouraging new life!!

  5. I have hatch-lings every year I have had to give fish away to many for my pond to stay Eco balanced otherwise. I used to think it was raining but soon learned it was the babies.. waiting to see if any arrive this year as I think the culprit didn’t make it this past winter. I have a mix of shubunkins and goldfish only so maybe that’s my problem with the excessive fish population lol …

    • I totally relate to your problem! When we first set up our pond I was not ready to invest in Koi, so I got a couple of Comets – I think I started with 3. They were a joy to watch, especially when the would jump above the water….little did I know! Every year I had tons of babies and soon could not give them away. Eventually as the older ones died (or were kidnapped by the herons), I replaced them with Koi & was happy that I didn’t have the breeding dilemna any longer…except for this one time.

  6. This has happened 3 times for me and in all cases it was a total surprise. I was looking at my fish in the pond and there was a tiny little one swimming with the school! Two did not survive but I now have a gorgeous black and orange koi hatched last year that resembles none of the fish already in my pond. It has grown tremendously and is a joy to watch him keep up with his much bigger brothers and sisters!

  7. About a month ago I noticed the Koi racing around the pond. They appeared to be chasing a red, white & black Koi and a black Koi with tint of orange. After racing around they would come up under the Water Hyacinth and and these 2 particular Koi flop on their sides. After watching from a distance, I moved closer to the pond. I then realized that with each flopping they were dispursing hundreds or thousands of tiny white eggs that floated to the sides and bottom of the pond, but I could not tell if they stayed in the Hyacinth. How long does it take? I do realize a very minute portion will hatch, but just want to keep an eye out. I also have a smaller Koi pond with 3 small Koi and it had hundreds of tadpoles. Slowly, I noticed them disappearing. Within a couple of weeks, I saw no tadpoles presuming the Koi ate them. With the larger Koi pond, I have Water Hyacinth, Water Lilies, and very small Iris’s. They have uprooted several plants so I have also tried floating planters. Perhaps if they survive, they will hide in those. I am NOT interested in breeding fish, but curious to know when and what to look for. Will they be sucked up the pump and into the filtering system? Any suggestions?

  8. Elaine,
    How many of each fish (Koi and Comet) breed did you have in your pond? When baby fish are growing up they are generally dark gray or even black in color for sometimes a very long time (So they are hard to see and less chance to be eaten by prey from above). They tend to change colors when they feel safe some faster then others. I get Comet babies with my koi as well in my 1000 gal. pond each year. They are “splattered” orange and black while they are still young. But, when they get a bit older they change to a more consistent color pattern to their breed. I think my babies are all Comets.Watch them grow and you will see their colors change quite often like mine. Still waiting for my koi to spawn. C.J.

    • I had 1 Koi & 1 Comet. Unfortunately the Comet died this spring, but they definitely got along last year! I got a better look at the baby yesterday and the shape seems more Comet-like than Koi, but I will definitely enjoy watching the baby grow and develop color.

  9. I believe my Koi and Comet spawned last summer. When we drained & cleaned our pond this spring, we found a small fish the size of which would correspond to it being born last summer. I can’t tell yet if it is more Koi or Comet because it is a dull color with just a hint of an orange sheen along its sides. I can’t imagine where else this fish could have come from other than from my 2 pond inhabitants. Our pond is about 800 gallons and is not near any other body of water.

  10. I have your Pond cleanup kit with Steps 1 through 4. After reading the directions, I am afraid to put in Algae defense (Step 1) because I am afraid it will kill my goldfish. They are about 5 to 6 inches long. What is your recommendation….just do steps 2 through 4?

    • If you have a smaller lined pond there are product out there such as the Defense Pac that offer the same benefits as the Clear Pac but geared for ponds with Koi and Goldfish. I would avoid using the Agae Defense but all the other products with the kit should be just fine to use.

  11. I have 100’s of tiny frogs emerging from my pond, but Thurs. morning when we checked the skimmer there were 5 dead frogs in there, and all about 5-6 inches…what happened to them? The fish, tadpoles and baby frogs all appear to be fine, so I’m wondering. The last thing I put in there was the muck away and the pond balance 3 weeks ago. The muck away is keeping the skimmer basket full of big clots of dead algae so we have to keep it emptied, and this is the first time we have seen dead frogs.

    • Liz,
      At this time of year, frogs are looking for places to hibernate for the winter and often times end up in a skimmer. The natural bacteria products that you mentioned are safe for aquatic life and would not be harmful to your frogs. Frogs absorb oxygen through their skin and it is possible with clumps of dead algae, that they were not able to get the required oxygen that they needed. Keeping the debris basket cleaned out and if you find frogs that are in hibernation, move them to another spot in your pond where they can safely spend their winter in hibernation.

      Here is link to a Pond Guy Blog: Where do frogs go in the winter?

  12. My koi are too prolific for the size of my koi pond. I want to get rid of most of the offspring (all sizes) but don’t know how. I think some may be goldfish as well although we did not place goldfish in the pond knowingly, I think one or two came in sold as koi.

    • Hi Arthur,

      Either manually netting fish out or using a fish trap can aid in physically removing the fish to another location or you may want to put a single bluegill or bass in the pond which would reduce the amount of offspring as well.

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