Pond-Water pH is difficult to measure and control.
You need buffering in pond-water .. hard water is better for pond stability
I have heard from two readers very recently who decided to make adjustments to their pond-water based upon pH measurements they made ... on this basis I thought let me go into this matter of pond-water pH more carefully because I know it can be confusing and even misleading and people adjust pond-water parameters in error as a result.
In general my advice is ignore pond-water pH unless you are a true enthusiast and prepared to measure the pH of your pond-water twice a day every day and graph the results.
Pond-water pH is an extremely complex pond variable. It is almost impossible to make an accurate adjustment even in the unlikely event you have measured the result correctly and you have taken the sample at the right time of day. So why measure pond-water pHit? .. well as I suggested; don't
There are mathematical reasons and chemical reasons for this difficulty ... the maths problem is due to logarithmic variability and not simple proportional or linear variability but we are already getting too complicated.
The chemical reason is the result of what is called "buffering" and that is what we will talk about.
Buffering is better understood by talking about hard and soft water which are terms most of us are familiar with.
Briefly buffering does what the word describes ... it buffers, insulates, minimizes, or protects pond-water against excessive pH variations in the pond-water due to changing acid or alkali content brought about by natural processes taking place in any fish-pond or planted pond.
If the pond-water is buffered then the pH does not change too much under normal day to day activities. Pond-water low in buffering capacity however can show large swings in pH during the day as plants photosynthesize for example in aquatic plant photosynthesis pond-water tends to become more acidic (lower pH) at night and less acidic (more alkaline) during the day.
In general buffered water (hard water) is normally better for pond inhabitants ... more in a moment but lets talk a bit about fish stress first ....
Fish become stressed when their living environment (the pond-water) changes significantly .... hence the recommended procedure for introducing new fish to pond-water you will all be familiar with I am sure ... i.e. let the temperature between the bag water and the pond-water slowly equalize by floating the bag on the pond and/or by adding small amounts of pond-water to the bag before releasing the fish.
Trying to make changes to water pH by adding chemicals of any kind introduces stress. When fish are stressed they become prone to disease from lurking bacteria which are always present in your pond-water. So do not create stress situations and you will lessen chances of bacterial disease problems. Large daily pH fluctuations also create stress.
HARD WATER ...
what is it? learn a lot more here
The easy way to recognize if general hardness exists in your house is by washing
your hands and face ... if it is difficult make a lather and if a scum is left
around the basin or bathtub then your water is hard. If your,
skin, hair and laundry is less bright than you would like it then you may
have a case of hard water.
If lather forms easily and there is a slimy feeling to the water then the water
is soft.
Of course you can measure hardness and this is probably one of those tests worth
doing on pond-water now and again... . but if you measure it make sure you
understand the result before making any adjustments.
In goldfish ponds it is really unnecessary whereas with prize koi then it is
worth doing with a high quality test kit because you need to understand your
pond-water intimately and how it changes every day.
When you measure pond-water hardness you are actually identifying the amounts of
calcium and magnesium hydroxides, carbonates and bicarbonates in the water ..
also called temporary hardness (because such hardness can be removed by boiling
water which releases carbon dioxide and leaves insoluble calcium carbonate
behind ... see the scale inside your kettle).
By changing to a different test kit you can measure other types of hardness such
as sulphates and chlorides ... referred to as permanent hardness.
Total hardness is the sum of both types of hardness.
In general it is good to have harder pond-water (hard due to carbonates) in your
pond because it assists greatly in controlling variations in pH and also
prevents metallic impurities (such as copper which then becomes insoluble)
becoming a significant problem for your fish. In addition hard pond-water helps
a fish to regulate its own metabolic processes and reduce stress somewhat. Hard
water is normally on the alkaline side of pH ... i.e. more than 7
To try and give you a feel for how much pH can vary in a planted pond or one
with algae growth (source of carbon dioxide during night) consider the following
general statement ...
If pond-water just before darkness falls has a pH of 8 and a low hardness of say
0.3 and carbon dioxide released by plants or algae amounts to say 5 units
overnight then the pH at dawn might be as low as 6.8 because the released carbon
dioxide is naturally acidic. Now if the same water with a pH of 8 had a hardness
of about 2.0 then by dawn the pH would have fallen to only 7.5 due to the same
amount of carbon dioxide being released. The hardness has "buffered" the water
from excessive pH fall.
This process reverses itself during the daylight hours. So you can see large
swings in pH result from low hardness values.
Yes water can also be too hard and this situation assists in the formation of
string algae or blanket weed which is a curse. In very hard water pond keepers
get excessive algae build up on the sides of ponds). Softening hard water
where you have string algae problems can help. You soften hard water
by mixing soft water ... e.g. from a home water softener unit (see
Pond Professors pages on this subject here) which many
homes have.
Water hardness can be improved by adding sodium bicarbonate and I have seen it
suggested that the best material is calcified seaweed ... here's a description I
found on the web ... Calcified Seaweed is a calcareous marine algae resembling
coral, known to marine biologists as Lithothalium Calcareum. It is dredged from
the seabed mainly off the Brittany coast, dried at low temperature and crushed
to a fine powder, which is readily assimilated by the soil. It contains about
46% calcium oxide, 5% magnesium oxide; sulphur, copper, iodine and cobalt and
some twenty trace elements. It is an ideal soil conditioner and clay breaker and
can be used on lawns, beds and borders as an alternative to 'lime' to correct
soil acidity. It is highly favored by chrysanthemum, sweet pea, dahlia, leek and
onion growers. It is non-toxic and safe to use does not scorch and stores well
if kept in a reasonably dry place