QUESTION NUMBER 3

3) Koi are entering the autumn season and all of the sudden the shiro Utsuri are looking better than ever! Why?

 This is an interesting one because it sheds light on environment and koi physiology and the profound influence that temperature, light and oxygen has on the koi – not to mention, the seasonal effect has on a koi.

So what happens in autumn?   

    The days get shorter and the nights get cooler. And cooler water also holds more oxygen.

 In addition, IF the temperature of the pond starts trending towards the low 70s and high 60s, this becomes the perfect environment for a koi’s metabolic efficiency.

 SO when we see our shiro utsuri ( the change is most noticeable in this variety) turn brilliant white and deep black, we are seeing a fish who’s metabolic rate is humming due to high oxygen levels and perfect metabolic efficiency. We are also seeing skin changes in the fish as seasonal effect takes hold. This is primarily in the endocrine system triggered by the light changes detected by iris and hypothalamus.

 The fish will also become what is usually interpreted as ‘hungry’ around this period of time. They do indeed feed more vigorously during this time as cooler water and changes in the metabolism stimulate appetite. Again the duel response of high ORP and seasonal cues. The koi’s biological clock knows winter is coming. Not the koi mind you! Just its biological clock and instinctual cues.

   It is best advised to not overfeed as the time for winter conditioning actually began in August!  But to feed slow and steady until temperatures stay below 50 F for a few days and night temperatures are moving into the low 40s. Each area is different so use your own powers of observation. But do consider the big picture which says, koi metabolically shut down at around 46F. They become ‘inefficient’ regarding how well they can assimilate nutrition below 50F. And inefficiency means that water quality will suffer.

  No koi ever died from being fed a day or two below 50 F. But koi die all the time from poor water quality below ice for 16 weeks.