Ph (Potential Hydrogen)
pH is a measure of the acidity/alkalinity of the pond water.
The pH logarithmic scale ranges from 0 – 14, where 0 is very acidic
and 14 very alkalinic. A pH of 7 is said to be neutral.
Pure water has a pH of 7. An ideal pH for Koi is somewhere
between 7.0 and 8.0. The pH scale is logarithmic so a pH of 8
is 10 times higher than a pH of 7, and a pH of 9 is 100 times higher
than a pH of 7. Because of this, it’s actually more important
to strive for a stable pH than try and hit between 7.0 and 8.5.
A pH reading of 7.0 in the morning and 8.5 in the evening is worse
than a constant pH reading of 9.0.
You should measure the pH of your pond water in both the morning
and evening every week. Each reading should be between 7.0 and
8.0 as above. The morning and evening readings should be roughly
the same. If this is not the case, you should take steps to
rectify the situation.
You should also test the pH of the water you use for top ups.
Obviously if this is outside of the ideal range then it will need
adjusting before adding to the pond else the pond pH will likely be
outside the ideal range! In general, when testing your pond pH,
you should find this is close to the pH of the water you use for top
ups.
pH below 7.0
The main cause of this is dirty filters/pond. The biological
action of the filter will also keep pushing the pH towards the acidic
side.
If your pH is low, you should test for Carbonate Hardness (KH) (see
‘beyond the basics’). Basically, KH acts as a natural buffer
against acidic decline in pH i.e it will stop the pH falling. As
it stops the pH falling, this buffering capacity gradually gets used
up. Once used up, the pH will begin to fall again.
The KH should be kept around 6 dH (107.4 ppm CaCO3). Higher is
ok and will provide a larger cushion for error (see ‘beyond the
basics’ for disadvantages of this). A KH lower than around 2 dH
(35.8 ppm CaCO3) indicates the KH has pretty much ‘run out’ and needs
to be topped up.
To top up your pond KH, first measure the KH of the water you use
for top ups. If this is > 6 dH then simply carry out water
changes to top up your pond KH. This is one reason why regular
partial water changes are so important.
If the KH of your top up water is lower than 6 dH, you’ll need to
add oyster shell to your filters in order to increase the KH. As
the oyster shells top up the KH, they will begin to dissolve.
Obviously when this happens, they’ll need to be replaced.
If either your top up water KH is low and/or you’re using oyster
shells, you should test at least weekly for KH in addition to pH.
There are some chemical products on the market that will instantly
increase/decrease pH. Unless it’s an emergency, I would not
recommend using these temporary solutions. They won’t last long
and will in fact create large pH swings causing greater stress on the
Koi
pH greater than 8.0
Koi can tolerate a higher pH far better than a low pH.
However a high pH should still be investigated and rectified.
The common cause of a high pH is a pollutant such as water running
into the pond from nearby brickwork/farmers fields etc. All
mortar around the pond should be sealed with something like G4 to
prevent lime leaching into the pond water. Lime will cause the
pH to rise.
Fluctuating pH – greater than 0.5
The pH in your pond can fluctuate from first thing in the morning
to late evening. It is normal to see a small fluctuation.
However, fluctuations greater than 0.5 should be investigated.
During the day any plant life (includes algae and blanketweed) in
the pond, through the action of photosynthesis, will consume CO2 and
release O2. This effect will cause the pH to rise.
Generally the greater the sunlight and hotter the day, the greater the
rise on pH. This is one good reason to keep your pond algae and
blanketweed free!
During the night, this same plant life will begin to respire.
During this process, O2 will be consumed and CO2 released. This
has the opposite affect and will cause the pH to fall. This is
another reason why O2 levels can become dangerously low at night!
|
