How things work: Clays and buffers in a Koi Pond.

When we view a pond full of koi, swimming and thriving in a high quality pond environment, we are in fact witnessing the product and embodiment of thousands of different microscopic processes that will never be seen by our naked eye. Every time a koi eats and digests its food, reactions occur within a koi at the molecular level, leading to the successful digestion, excretion or assimilation of its food. We do not see (or perhaps even appreciate) these micro-bioreactions, but nevertheless they are taking place and, with the evidence clear for all see it in the form of healthy, growing and colourful koi.

The same is true of any number of treatments that we might add to our pond to improve water quality or treat disease.
The more free hydrogen ions, the more acidic the water and the lower the pH.
In a natural pond, that is open to natural influxes of freshwater as well as the natural presence of specific minerals, then the pH will remain relatively stable.
Besides koi, heterotrophic bacteria and all invertebrate and plant life will also respire, releasing CO2 and adding to the acidification of the pond.
A buffer is the solution to this problem and is best thought of it as a 'mop' that soaks up free hydrogen ions.
The most common buffer in koi keeping is calcium carbonate, or materials that contain calcium carbonate such as limestone chippings, Cockleshell and even calcified seaweed.
It is widely recognised that koi exhibit their best health, colour and vitality when they are kept and reared in a clay pond (often referred to as a mud ponds).
The water is highly turbid as koi forage in the muddy substrate, stirring up the ultra-fine clay particles, keeping them in suspension.
As you will see from the Niigata mud ponds, the clay particles are so fine that they do not settle but remain permanently in suspension.

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