Simply Koi and More Koi

Hey there,

I was experimenting with kH and maintaining a low kH value. I did not have any pH crash. Why?

I had lower than 1 kh.

Having a low KH doesn't guarantee a pH crash as long as the value stays above zero.

Many koi keepers who use RO water to emulate conditions in Japanese mud ponds run at (frighteningly) low values of pH and KH. If you get the balance right, you can even run with a pH just below 7.0 . The only caution I add to that is that no one should try to run at those values without understanding how close they are to a slight reduction in KH leading to a full blown pH crash and that running at low values is only safe if sufficient extra care is taken to keep the KH topped up to the chosen value. Otherwise, it's a perfectly valid way to manage pond parameters.

The greatest cause of a reduction in KH is that filter bugs, between them, use over seven times as much KH as the ammonia they process through nitrite and into nitrate. That must be topped up to maintain the value or else a crash becomes a near certainty.

For koi keepers who prefer an easier life, without the need to pay constant attention to a KH value that is barely above zero, the recommendation is to keep the KH around 5 to 7 dKH (90 mg/L to 125 mg/L) and accept whatever pH that brings. That way, there is a big safety margin before the KH is at a risky low value.

If you want to experiment with low values of KH without endangering the fish, there's a way to increase the accuracy of the standard test. Use ten times the recommended volume in the test sample and then each drop will indicate 0.1 dKH rather than 1 dKH and you will be able to get the value to the nearest 0.1 dKH rather than to the nearest 1.0 dKH. But don't forget to keep a close eye on the value especially after feeding.