Pond water quality is what keeps your fish alive and healthy
Water quality is a very difficult concept to grasp when it comes to fish keeping. Clear water does not necessarily mean high water quality
You look into your perfectly clean and clear pond, you see fish darting around, they come to your hand to feed having lived happily in their home for well over 2 years. The plants are growing well and you are pleased with your investment and especially that you have never lost a fish. This desirable situation is made all the more possible when you understand something about water quality and what is happening in a pond.
The fundamental and single most important factor behind good water quality is excellent biofiltration. Poor filtration will undoubtedly create poor water conditions that in turn will result in water looking poor, fish disease and possibly even fish deaths.
There are specific parameters that indicate good or not so good water quality.
Water Quality More Advanced Considerations
The following parameters are important in good pond keeping in addition to the absolute need for biological filtration:
High levels of oxygen
Low variations in pH of the water
Good levels of carbonate hardness
The absence of pathogenic bacteria
The vital importance of Oxygen
Most of us in South Africa live in higher altitudes where the oxygen concentrations are lower than at sea level. This is why our cars go faster at the coast and we go to bed early in Johannesburg. If we lived at 12,000 ft we would get even more tired. On top of Everest we cannot breath without assistance.
Fish are like that and so are bacteria. Starve them of oxygen and they suffer just like us.
Peter Waddington who is probably the world's most famous koi keeper spent a week doing seminars for me in South Africa about 5 years ago. If I learned nothing else during all those seminars I attended with Peter as my guest it was that you couldnt overdo the addition of oxygen/air to any pond containing fish.
Peter's own pond and filter literally bubble with air which is continuously pumped into the circulating water, the filter and the waterfall as well as the pond 24 hours a day 365 days a year.
There are some things you really do need to know about what happens to the oxygen concentration in your pond under different conditions. In this short discussion I will state matters factually and illustrate by numbers where I can:
Water can hold less oxygen the higher the temperature rise in the water.
This means that in January (Southern Hemisphere mid Summer) there is much less oxygen in a pond than in July when the water is much colder. This is why trout need cold water - they need high levels of oxygen that they cannot get in warm water. Koi and goldfish would thrive on 4ppm levels dissolved in water whilst trout need 20% more.
Oxygen is introduced to water at the pond surface and by any mechanical means such as use of a fountain, waterfall or air pump.Aquatic plants also play a role here.
At 10 deg C (50 degrees Fahrenheit) at sea level water can hold 10.9 mg/litre of oxygen. At 20 deg C it can only hold 8.8 mg/litre and at 30 deg C the saturation level is 7.5 mg/litre. Dont worry too much about the actual number just focus on the significant reductions.
In practice few systems reach these saturation levels and this is the reason Peter Waddington blows massive amounts of air into his pond and filter in order to get as close as possible to saturation.
Plants are always a good idea in a pond because they introduce oxygen into the water during the daytime parts of the 24 hour daily photosynthesis cycle.
At night the plants reverse this process by using up oxygen from the water and converting it to carbon dioxide and then to carbonic acid.
This is another reason for maintaining pump flow 24 hours per day so that circulating water continues to pick up oxygen and distribute it throughout the pond during this night time period.
I have previously made the point that in ponds where high levels of algae existed then these algae could totally deplete a pond of oxygen overnight causing fish loss. Large fish tend to suffer first
In summary you cannot overdo the introduction of air into a pond.
In a swimming pool if you measure the pH at noon and again at midnight it will be the same. In a pond with plants it will not be the same because of the photosynthesis cycle.
During the night the pH will fall before rising again during the day to its original level. With high levels of algae the pH can change dramatically with dire consequences.
pH is a measure of the acidity or alkalinity of water. The measurement scale is from 0 to 14. At the mid point of the range the water is neutral since the acid and alkali balance each other. This is the case for pure water.
Less than 7 the water is acidic (vinegar is less then 7, a lemon is about 2.2). More than 7 and the water is alkaline (sodium carbonate is a good example and milk is between 7.1 and 8.5).
Stable levels of pH are desirable and a range between 7 and 8.0 is good for a pond. When you start seeing levels of 9 there is a danger developing.
PH, even though it is simple to measure is a highly complex phenomenon. pH has a great influence on almost everything in a pond environment. It effects how the biofilter works, it affects the fish, it in turn is affected by the addition or removal of pond water and whether the water from the tap in your region is hard or soft. At higher pH levels toxic levels of ammonia become deadly.
To have a high level of control over pH fluctuation it is important to have a good level of hardness in the pond.
Continued water quality pH and water hardness
This web page is an extract from Tony Roocroft's "The Complete Pond Solver" ...
you can read more about it at
http://www.really-useful-books.com ... when you buy the book you get 12
Excel pond calculators free as well as "Water Lilies and Pond Aquatics" ebook
also free.