SF Bay Area Koi Club

Organization of Pond and Koi Keepers




Why are my Koi yellowish, instead of white?

12/07/2017 1:22 PM | Anonymous member (Administrator)


Ah - the dreaded yellowish looking head...  One of our K.O.I. nutrition students recently asked why some Koi have yellowish skin, rather than pure white.  Here are some of my thoughts about yellowish skin...

The quality of Koi food DOES matter!  For years, I used cheaper food, and was quite happy with the results.  My Koi never looked perfect, but I just chalked it up to poorer genetics...  Then I started some experimentation with different foods.  I don't currently have any show Koi, so figured I should learn as much as possible with the Koi I have...


My first experiments started when I was building my monster pond.  I had 12 Koi in a show tank in the basement for 3 years.  I fed them different foods for 6 months at a time, and noted the results.  I discovered that the effects of foods vary considerably!  Koi develop different body shapes, the food affects color, and there is certainly a difference in the amount of waste the Koi produce (poop) depending on the food!  In the 3 years, I put on over 12" of growth on each Koi in less than 400 gallons of water - they grew from about 14" to 26-30"!  That's a LOT of fish in very little water!  I did it with 50% water changes, and blasting the bead filter with 120 psi air for 5 minutes a day.  I learned that biobugs are not easily affected by filter cleaning, and that ShoKoi produced the least waste of any of the foods!  None of the Koi had good whites - and I was told that was because of lack of sunlight - I just had a grow-light over the tank...  Now, I think it had more to do with the food, and the fact that they didn't spawn in the tank...


Once I got the monster pond up and running, I bought some small Koi, and played with different foods to test growth rates.  The standard food used by most high-end Koi keepers is Saki Hikari.  Every other food is compared to that.  I tried a high end food provided by a breeder - and the Koi didn't like it, plus it was super-oily and did horrible things to my water quality!  I tried Purina Koi feed (Mazuri) - and the Koi had poor body shape and didn't grow properly.  Saki Hikari was OK - sorta middle of the road.  They Koi ate it, and they grew, and they looked OK.  Then this year, I tried a new food just imported in the USA.  Called JPD Shori - there is a another blog article about that food.  Turns out that JPD is the largest producer of Koi food in Japan!  Shori is their premium food.  WOW - huge difference!  The Koi loved it - they now wait in the feeding area an hour before each feeding!  And suddenly, these middle-of-the-road Koi looked AWESOME - you can't believe the difference in the whites - instead of slightly yellow - they were fluorescent white!  Which of course makes all the other colors just shine!  The reds look more intense, the blacks look blacker - even the yellows had more intensity of the pigment.  Go figure!  You never could have convinced me that one factor - food - could make THAT much difference - but it did!  Of course, it could be some combination of my water quality and the food.  Maybe Shori only works with my water quality?  Some of the high-end Koi keepers in my area are going to test it next year, and then we'll know if it's a one-time phenomena, or if it's something that's repeatable in different circumstances.


As you know, there are LOTS of other things that affect the quality of the white.  The biggest is Nitrates.  If you can keep Nitrates down below 5ppm, then any yellowing of the skin is coming from another problem.  Koi that have been sick, and have compromised liver or kidneys become yellow.  Color foods generally make whites look pink in my experience.  I associate yellows mostly with poor genetics.  When young Koi become mature, and they spawn for the first time, I always find they look better the following year after the spawn.  The eggs and sperm seem to collect unwanted pigment from the rest of the Koi, and once the Koi has spawned, the Koi is left much whiter.  Egg-bound females are almost always yellowish... Water changes seem to have the biggest affect on whites - because of the nitrate reduction.  Plants also reduce nitrates - but somehow, Koi in plant ponds never look as good as those in ponds with massive water changes...  Koi in mud ponds with green water usually have awesome colors - especially red - from all the algae.  Whites can look awesome in mud ponds, or not - I suspect it depends on the water chemistry.  And last, stress really affects how Koi appear...  Some fish stress when you look at them!  LOL  Some have compromised genetics so their organs never grow properly, and they die before they are 6 - meanwhile their whites appear yellow.


So, if your Koi appear yellowish - go down the list of likely suspects.  Switch to a premium Koi food.  Check nitrates.  If you have anything over 5 ppm Nitrates - do a LOT more water changes...  Did your Koi spawn this year?  If you can check all these boxes, then I'd guess it's just genetics.  You really do have to look at bloodlines when you buy - but the great news is that there are now tons of really good bloodlines, and you can get $30 Koi that have fluorescent white - although they all have plenty of other problems that prevent them from being show fish... 


I guess that's why this hobby is still so fascinating after 30 years!  There's always something new to learn, and the Koi are incredible teachers!  Experiment with your pond and have FUN leraning!  To me, that's what Koi keeping should be all about!


©2014-2018  SFBayAreaKoiClub.org  All Rights Reserved.
Powered by Wild Apricot Membership Software