Some people advocate maintaining crazy levels of KH within the
pond. I have never managed to fathom out why?
KH (otherwise known as alkalinity or carbonate hardness) is simply the level of ions present in the water that are capable of ‘mopping up’ acids.
There is a myth that biological filters need KH to survive. This is completely incorrect! Filter bacteria feeds on fish waste and organic matter. In the process of breaking down this matter, acids are produced. These acids are neutralised by the bicarbonate ions, which are alkaline. This keeps the pH from turning acidic.
It doesn’t matter whether there is 20mg/l of KH in a pond or 100mg/l, it won’t affect the filter or koi in any way. In fact, if the KH is too high, your pH will ride too high.
Remember, KH is purely an acid neutraliser, not a filter food source! What does matter however is whether your KH level is stable from day to day or month to month. If you find yourself having to buffer your KH, then it
is most likely because you aren’t changing enough water.
As far as running low KH levels are concerned, if your pond is working efficiently and there is no trapped decaying waste in the system, then you will find that even after going away on holiday for a couple of weeks, you would see very little change on your return. It is also important to
realise that even with high KH levels, it is still possible to induce a pH crash, particularly if the pond is covered.
