Koi

The term pH is used to describe how acidic a substance is. Technically, it describes the number of hydrogen ions, which is what an acid is. Because the numbers involved are so long-winded, a scale was developed to quickly describe the concentration of hydrogen (H) in a substance.

In fact, the pH scale describes the amount that H is diluted and it runs from 0 to 14, with a dilution of 10 times for every unit of the scale (called a logarithmic scale). So, a pH value of 0 means that the H is not diluted at all and the substance is extremely acid. Whereas something with a pH of 14 means that the H has been diluted a huge amount (10, times 10, times 10, and so on, 14 times!). Such a substance cannot be called acid anymore so is described as alkaline or (more correctly) basic. The middle ground of the scale – where the substance is neither acid nor basic – is called neutral, with a pH of 7.

Most water is around neutral, although some areas of the UK might have slightly acid water (around 6), and many areas might have a pH of around 8. Koi are quite happy anywhere within this range, however, due to the relationship pH has with other water characteristics, it’s best to have the higher (more basic) conditions.

Too acid or alkaline conditions produce similar symptoms in  fish (called acidosis and alkalosis respectively) and include lots of slime (mucus), washed-out colours, laboured breathing and rubbing itself on the pond edges. Increasing pH levels is very easy – add limestone chips, mussel shells or oyster shells and so on (pop them in the filter). Reducing pH levels is much more difficult but there are commercial substances available.

Nevertheless, a very high or low pH means that something else is not right with your pond, so you must fix that first. Whatever you do, seek the advice of your Koi retailer and make any changes very gradually.

Written by Adrian Love