Thread: Fish Death - Help needed please!

If you have a limestone in the pond or waterfall and you have high dissolved carbon dioxide (CO2) then the calcium carbonate in it will dissolve into the water and raise the KH. However, since the rate of dissolution is highly dependent on the level of dissolved CO2, this will not reliably buffer the pH to any stable value in the koi keeping range because the target pH of dissolved calcium carbonate is in excess of 9 pH and this value is achieved with high levels of dissolved CO2.

Since aerating water not only adds oxygen but also drives out CO2, a highly aerated pond will only have a very low level of CO2 which will make the rate of dissolution very slow. Therefore the raising of the KH and the resultant rise in pH will be unpredictable.

Sodium bicarbonate is a much more predictable way of raising the pH as I explain in my article on my website on the link below.

I've tried to make this explanation and the article on my site simple to understand but this subject is very technical so please ask questions if it doesn't make sense.


https://www.mankysanke.co.uk/html/alkalinity.html