Garden Action

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Maintaining a Water Garden

Careful planning in siting, construction and the correct balance of water, plants and fish will ensure water gardens are trouble free. From time to time, repairs will have to be carried out if the pond is damaged or leaks. Algae must be controlled and plants divided from time to time.

Constant or sudden water loss indicates a leak and it will be necessary to drain the pond to carry out a repair.  Fish and plants must be placed in an alternative container, a cheap children’s pool may do.  Allowing the water to drain gives an indication at which level to look for the leak. Ponds can be further drained by pumping or siphoning after the leak is found.  With a watercourse, turn off the pump and see which part drains first, the header pool or the base pool.  If the level of neither of them drops, the watercourse may be leaking.

Flexible liners
Leaks may be caused by the edge of the liner moving or by punctures.  Assuming the puncture has been found, thoroughly clean the area around the leak. The hole can be repaired by double sided tape made for the purpose that can be bought from suppliers.  Roughen the surface around the hole with a piece of sandpaper to help adhesion. The tape is used to fix a patch over the hole and the pond can be refilled after an hour. PVC liners can be repaired with adhesives and patches.


Preformed pools
An incorrectly supported pool can crack under the weight of water.  Cracks can be repaired with a fibreglass car body and boat hull repair kit.  Follow the instructions and make sure the base is adequately supported to withstand the pressure.

Concrete pools
Concrete pools leak through cracks caused by ground movement.  Water will escape through very fine cracks, so inspect carefully.  A fine crack needs to be enlarged, thoroughly cleaned of debris and sealed with mortar or waterproof filler.  Leave the mortar to dry before painting with a sealant.

Water should remain clear after a balance of plants and animal life is achieved.  The balance may be upset a further introduction of plants, fish or water from another source. Algae are simple plants that survive on sunlight, dissolved nutrients and carbon dioxide. Like other plants, they also need oxygen to respire. An increase in their number causes a ‘bloom’ with negative effects on pond life. Bacteria decompose plant matter, releasing more nutrients and consuming oxygen. Their numbers can be controlled by limiting light by growing enough plants to shade the depths and removing leaves or plant matter from the water.  Avoid the use of fertilisers close to ponds, making sure there is a margin that absorbs any runoff into the water.

A number of processes can discolour water, algal growth, leaf fall or animal activity. Newly established pools go green as a result of algal growth and may resolve itself in a short time. Tea coloured water results from staining by tannin from fallen leaves and is harmless. Fish and birds, particularly ducks, will stir up water which can be settled by adding gypsum to the water.
Ponds should only need cleaning every few years if they are kept clear of leaves and plants kept trimmed.  Organic matter should be removed and the water balance restored soon after. Blanket weed, an alga, can be removed with a garden rake.  Decaying matter reduces the oxygen content of the water.