Temperature adjustment for Koi

Koi can handle a wide temperature range from as low as 4C up to as high as 30C. However as with all fish, rapid changes in water temperature are not a good thing. 1C down and 2C up is the rule.

But what does this mean?

Simply put, safe temperature adjustments for Koi are that it should take 1 hour to adjust by 1 degree Celsius down and one hour to adjust by 2 degrees Celsius up. In other words Koi prefer going up in temperature as
opposed to going down…

And don’t we all?

But when fish arrive from Japan in plastic bags that they have been in for 36 hours and the water is vrot, temperature is less of a concern than the rotten water. So we balance matters by adding water to the bags and matching the pond temperatures to the bag temperatures before the fish arrive.

So now you know. Stress free temperature adjustments must be done slowly. Temperature stress can lead to breakouts of whitespot – the most common parasite to pop up when there have been wild temperature swings.

We have also heard of cases where a severe hail storm has resulted in the death of Koi - ostensibly due to the sudden and dramatic drop of the pond water temperature. In a shallow Koi pond Koi have no escape to the bottom of the pond where generally the water temperature is likely to be more stable. Also if the filtration turnover rate is quite high (normally a desirable thing), the temperature drop is likely to be further accelerated.