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16 October 2014
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John Cushnie On...

No Green Water
1 April 2006

Pic: Garden PondSparkling, clear water reflecting the poolside plants and fish darting about. That is the image of a garden pond and it can be the reality but only with dedication and common sense.

Still water will become stagnant unless oxygen is present and a balance is achieved by introducing plants and wildlife. Sunlight encourages green algae and a single, minute plant of pond weed will become a sheet of green within a very few days.

Leaves and debris will accumulate in the pond forming a layer of decaying material at the bottom.

There are simple ways of avoiding many of the problems and undoubtedly, in the case of a garden pond, prevention is better than cure.

A waterfall, cascades or a fountain will bring oxygen into the water and discourage discolouration. Oxygenating plants breathe out oxygen through their leaves but do be careful. Most of them are very vigorous needing to be thinned several times during the season otherwise they will take over the pond.

Wild Life

Pic: NewtEncouraging wild life such as frogs, water snails and newts will help achieve a balance in the water.


Green Water

Pic: Water Lillies There is nothing more unsightly than green water. It thrives on sunlight. Shading 50 % of the water surface will reduce the risk. The leaves of water lilies are large and will help provide that shade. Growing plants close to the pond on the south and west sides will cast shade where it is needed most. Another method of control is to pack a fine mesh bag or pair of tights with barley straw and submerge in the water. It will be 6 weeks before it starts to have an effect and should be removed in the autumn and the straw spread on the compost heap.


Apart from water lilies and oxygenating plants other aquatic plants will, through their roots, help to remove impurities. Weeds such as duck weed are a real nuisance. It can be introduced on the feet of ducks or even frogs but in most cases I believe it is brought in with free plants from friends. Wash incoming plants thoroughly and place in an isolation bucket of water for a week to see if the dreaded duck weed is present.


Pic: Autumn Leaves The only sure way to eliminate autumn leaves from the pond is to cover it with a net during the “fall”. At other times the odd leaf will cause no trouble.

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