Waterfalls, venturi’s etc are all well and good but the reality is they only provide a fraction of whats needed, and the only way to ensure O2 levels are sufficient is by using air pumps to ensure there’s enough! The amount of oxygen your pond is able to absorb and retain primarily depends on two factors: temperature and atmospheric pressure.
As water temperature increases its ability to both absorb and retain oxygen decreases. This is also true of atmospheric pressure. If you live at a high level above sea level for example in Johannesburg in South Africa, Denver in the USA or on top of Ben Nevis in Scotland, the elevated atmospheric pressure makes it more difficult for the water to absorb and retain O2. That means you have to work hard to get it in, and keep it in!
That also explains the atmospheric phenomenon sometimes experienced in the UK in summer, when air temperatures and thunder storms or other low pressure events suck out the air from our ponds, and Koi start gasping at the surface. It’s a fact that more Koi die in the summer in UK ponds from oxygen depletion, than they do from the cold in unheated winter ponds!
But the Koi are only half the story when it comes to O2 dependency, and they’re not even the biggest half! Koi are sensitive to oxygen levels but the vital nitrifying bacteria in our filters are not just sensitive, but simply can’t survive without it. So the first thing affected in our ponds if O2 levels drop are not the Koi, but the bacteria in our filters, and that means the water quality suffers. For our Koi, thats a double whammy, but where O2 levels can quickly be restored, and the Koi quickly recover, that’s not the case for the nitrifying bacteria in our filters. Once they die they die, it takes time for them to be replaced and the population to recover, and that means our water quality suffers for a much longer period. The impact that has on our Koi, can be even more detrimental.
O2 levels in Koi ponds really are non negotiable. Just like us, our Koi, and our filters require sufficient oxygen all the time, and as with most things that’s down to us to provide, deviate at your peril!
When it comes to oxygen levels and our Koi, there is no choice. We need to get it right and keep it right, and we need to do that permanently! …Paul White
