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Why do Koi (and Goldfish) Change Color? – Decorative Ponds & Water Gardens Q & A


Why do Koi (and Goldfish) Change Color?

Why do Koi (and Goldfish) Change Color? Colin – Sunbury, OH

You’ve now created the perfect pond habitat and begun to add fish. Multiple trips to the pond store scanning the tank to find just the perfect one to bring home. Some have spots, some red, some orange with black streaks. At least you’ve found the perfect one, black and white pattern with orange freckles on the face. You make your purchase and carefully introduce your new friend to the pond. Everything is going great until one day a few months later you notice that those freckles disappeared and the perfect pattern is changing to white. What happened? Did the fear of the heron turn him white as a ghost? Is there something you did wrong? Luckily, most of the time it’s nothing too serious. Let investigate a few possible causes.

Sun exposure: If you are in a climate where you experience a cold winter and your koi have been hiding out in your pond waiting for spring you may notice your koi are a little lighter in color once the spring time thaw sets in. This is common because koi do not receive a lot of exposure to the sun over the winter months. Once they get back into the routine and the sun begins to shine this color will usually return.

Genetics: Most koi come from parents that were not identical so the same rules apply. Some coloration is dominant and some recessive. This could also change with time the same way your hair color changes. Someone born with red hair may turn blonde or brown as they grow older. This is just a natural part of growing up.

Stress: Stress factors such as predators, parasites, water chemistry or water quality may affect coloration. A quick change in pH due to overwhelming organics or over population would cause a stressful environment which may cause a color change. Be sure to test your water, address water quality issues if necessary or treat the pond with pond salt, pond and fish conditioner or fish disease control. Watch your fish for behavior clues to determine if they are stressed.

Food: What type of food do they eat? Inexpensive bulk food may not contain as many vitamins and nutrients which may affect coloration. This does not necessarily mean the fish are unhealthy but they may not be receiving enough vitamins to support their color. Try feeding them food such as Pond Logic Growth & Color fish food, which supports coloration or even include fruits and vegetables such as oranges. Koi will love the citrus and this could greatly enhance their color.

Once you’ve addressed all these possibilities sit back, relax and enjoy your koi. The color may have changed but their playful personality will still be the same!

POND TALK: Have you ever had your koi change color?

Aerate your pond

21 Responses

  1. I just brought my koi inside in Dec and 3 of them have alot of black color that gradualy appeared on them…..at first I thought it was an algae on them, but it definately is a color change. By reading the above posts it is not uncommon. Maybe when they are moved back to the outdoor pond they will get their orange back.

  2. I was told that my koi would change color when he got around five years of age, he is a fry he was a a gold, but he is now around a year and is changing into a black. I have tested the water and have him on the proper food. What I wanted to k.ow if that was normal, or well I think it is wonderful, but I want to make sure he is fine.

    • It is normal for Koi to change color due to a variety of reasons. Often times their genetics play a big part in their developing colors. Their exposure, or lack of, to sun can cause a change in the intensity of their colors. Their fish food may be fine as a feed, however it may not contain the “extras” that brighten and maintain their color. Look for foods that contain color intensifiers and vitamins in them.

  3. i bought a light yellow butterfly koi, now he has a gold head and some gold down the side of some of its body but from the head back its black. i think it looks pretty awesome. im a young new home owner that inherited a few koi fish ponds and i absolutely love it. when i was real young i used to always ride my bike to the nearest pond and catch frogs or something, you know be a kid. so i built a waterfall so that the smaller pond flows into the bigger pond. it was pretty sweet. only problem is the stones on the waterfall grew a lot of algae and the bigger pond became very mucky. i am currently in the process of removing the waterfall feature and just having my koi in the big pond. i am no expert on koi but if i had to give my “expert” opinion i was say make sure you feed your fish about twice a day and clean your pump filters once a day. there are not many moments that i enjoy more then grabbing a coffee and feeding my fish. rock on!

  4. I left on a weekend trip and had no white goldfish. When i returned I had 1 completely solid white goldfish and 1 almost white but with a couple of small orange spots. These two are about two years old About a month ago I introduce 2 koi and 4 goldfish much larger than the 2 and 3 year old goldfish I already had. I read somewhere that the introduction of new fish can cause an established goldfish to change colors. There have been no other changes to my pond. Am curious to know if this the introduction of new fish could cause a goldfish to change colors.

    • Hello, in my experience while either introducing new fish or just over time, certain fish would change color depending on their mood. I would assume as humans do, blush, turn pale, etc. The same occurs with fish perhaps one has become an aggressor dominant alpha in the tank and others are lessor. Watch their demeanor, personality, does the more colorful, darker one pick on the smaller ones?

  5. I had a baby from last year black and orange. Color was 50/50. He is now 99% all orange. All his black disappeared. He used to be so cool looking. Now he is average orange guy. Still love him tho.

  6. I just bought a koi fish yesterday, out of 16, i only got 2 that were greater than 8″ this was the only black koi i chose. It had a single orange spot on the top of its head, today it is as if they black and orange switched, at first i thought i was looking at a different fish but i stood for a few minutes and knew it had to be the one. What happened?

    • You’ve now created the perfect pond habitat and begun to add fish. Multiple trips to the pond store scanning the tank to find just the perfect one to bring home. Some have spots, some red, some orange with black streaks. At least you’ve found the perfect one, black and white pattern with orange freckles on the face. You make your purchase and carefully introduce your new friend to the pond. Everything is going great until one day a few months later you notice that those freckles disappeared and the perfect pattern is changing to white. What happened? Did the fear of the heron turn him white as a ghost? Is there something you did wrong? Luckily, most of the time it’s nothing too serious. Let investigate a few possible causes.

      Sun exposure: If you are in a climate where you experience a cold winter and your koi have been hiding out in your pond waiting for spring you may notice your koi are a little lighter in color once the spring time thaw sets in. This is common because koi do not receive a lot of exposure to the sun over the winter months. Once they get back into the routine and the sun begins to shine this color will usually return.

      Genetics: Most koi come from parents that were not identical so the same rules apply. Some coloration is dominant and some recessive. This could also change with time the same way your hair color changes. Someone born with red hair may turn blonde or brown as they grow older. This is just a natural part of growing up.

      Stress: Stress factors such as predators, parasites, water chemistry or water quality may affect coloration. A quick change in pH due to overwhelming organics or over population would cause a stressful environment which may cause a color change. Be sure to test your water, address water quality issues if necessary or treat the pond with pond salt, pond and fish conditioner or fish disease control. Watch your fish for behavior clues to determine if they are stressed.

      Food: What type of food do they eat? Inexpensive bulk food may not contain as many vitamins and nutrients which may affect coloration. This does not necessarily mean the fish are unhealthy but they may not be receiving enough vitamins to support their color. Try feeding them food such as Pond Logic Growth & Color fish food, which supports coloration or even include fruits and vegetables such as oranges. Koi will love the citrus and this could greatly enhance their color.

      Once you’ve addressed all these possibilities sit back, relax and enjoy your koi. The color may have changed but their playful personality will still be the same!

      -Missy

  7. My white fish started to get red on their backs I just hope there not sick. . . .

    • Hi Mallory,

      As long as it just looks like discoloration then you are probably fine, just keep an eye on the fish to make sure it doesn’t develpe into something more.

  8. We are getting duplicate copies of your magazine, and the post office box is closed. Please eliminate the address of P.O. Box

    • Carol, I’ve marked the P.O. Box as Do Not Mail….it may take a cycle it to pull through the system but you should stop receiving catalogs to the P.O. Box.

  9. Without using harsh or expensive chemicals , I read somewhere that common household baking soda can buffer a pH swing in a pond . Don’t quote me though. Maybe some one else read the same article.
    If you have city water and are topping it off often that would explain your jump. Also if your fish food or plant fertilizer has high amounts of phosphorus – that would be my best guess as to what is adding to the problem.

  10. My PH is always bouncing back to a high reading. How do I stabalize it or buffer it? What product do I use? I get it lowered and then in a few days its back up way to high that even my plants die. Help please.

  11. I have some large goldfish. One of them seems “pregnant” Its belly is very very fat. It does not seem sick.
    Anything I can do to cure him?
    Thanks; Maria Christopher

    • Hi Maria,

      If the goldfish is pregnant there is nothing to do, it will happen on it’s own. As long as the fish is happy just continue to keep an eye on them.

    • Two of my goldfish (They are all about 10 inches long) is very fat, probably like yours. But very oddly, I consistently find one of them near the top of the pond upside down–not on its side, but completely upside down. Its underside (now topside) is right at the surface. The first time I saw this, I thought it was dead and began to scoop it out with a small net. The fish turned right side up and swam slowly toward the others. This has happened perhaps a dozen times this winter. What is going on?

      • Hi, it may have constipation or “swim bladder” problems. I could make recommendations or link you some sites to research, but i’d recommend you search for remedies on your favorite search engine instead as there are too many.

    • I have a couple of goldfish who have big big bellies. I finally asked the dealer who sold them to me, and she said it was simply the breed.
      They are “Fancy.” They should also have kind of a ‘winged’ tail also. I hope that this helps.

  12. I bought a solid black goldfish. Within a year he changed, gradually, to solid gold.

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