Treating Water for the Garden Pond
To most people, water is a simple liquid with a chemical basis of two hydrogen atoms combining with one of oxygen; but in nature it can vary considerably, as natural water contains other chemicals and organisms that can change its properties. Those waters with a high lime content are referred to as hard water, whereas low lime waters are referred to as soft. This is due to rain falling on soils that have a high or low lime content and picking up minerals as they filter through the layers of. Near volcanic vents, the minerals saturate the water to produce very unpalatable waters rich in sulphur or magnesium.
Tap water may also have other additions; chlorine and fluoride are probably the two best known, but even in soft-water areas some authorities add lime to make the water less acid. Rain water can present problems if you live to the windward of certain factories that emit fumes with a high sulphur content; these fumes can combine with water vapour in the air to form sulphuric acid and cause what is known as ‘acid rain’, which has cleared lakes in Scandinavia of fishes and plant life, leaving the water a clear blue but totally devoid of life.
The quality of pond water
If you want to keep fishes, water is a vital factor, and it must be able to support life without causing suffering. To use tap water, it is necessary to allow the chlorine to disperse, which it will do if left for a week or so before any plants or fishes are introduced into the pond. There are various forms of testing kits available that have been developed for aquarium use, swimming pools and soil testing, and these can be used to register the chemical level and the balance of acidity and alkalinity of the water.
A simple test is to watch the health of the plants and fishes: if they thrive, the water is reasonably balanced; but if the fishes become a poor colour, show no sign of growth and move sluggishly, then the water is suspect. If water is left static, without stirring or being moved, it becomes stagnant. The mineral salts in the water act together with sunlight and encourage the primitive plant life called algae and the proliferation of free-swimming green organisms, which make the water look green; eventually they die and start to putrify, using up oxygen and producing toxic gases. On the other hand, if the water is partially shaded to keep out some of the sunlight (usually by growing plants that will cover some of the surface), and organisms added that compete with or eat the algae and green organisms, the algae will be kept to a permissible level, covering the pool walls and stones but leaving the water clear.
An electric pump is normally used to force the water to a higher level, so that it returns naturally to its original level over a waterfall. Alternatively, it can be ejected into the air through a fountain nozzle. These methods both cause the water to break up into droplets, which have a large surface area and can pick up more oxygen; this oxygen-enriched water is excellent for supporting pond life.
Avoid making the water too rich in nutrients by feeding thewith ordinary fertilizers, manure or humus, as this will encourage the growth of algae; instead, keep to those fertilizers made exclusively for aquatic use.
Another problem that can occur is the draining into the pool of water from surrounding areas of grass and vegetation, bringing with it chemicals that have been used as fertilizers, or for killing pests, diseases or plants.
Depending on the nature of these chemicals, the water can cause either temporary or permanent damage.
Most modern chemicals are checked for toxicity and are passed for domestic use only if they have been proved perfectly safe when used as instructed. However, old chemical sprays and treatments are still available that can cause pollution in the garden pool. Where possible make sure that any natural drainage into the pond is diverted to drain away in a place where damage will not occur. When using sprays try to ensure that the fine droplets are not carried by the wind into the pond.