How bad is algae to garden ponds?

Two week-ends ago we had an Open-Garden in our village. The gardens we visited were all meticulously landscaped and all blooming in a variety of colour. Interestingly, they all included a garden pond in their landscaping and in two cases there were fish ponds flanking either-side of a feature foot path.

All were lined with a pond liner and edged off neatly. The only criticism was that the ponds were either covered in blanket weed or the water was so green. In some cases the ponds did not appear to be as well cared for as the surrounding garden. The ponds had few aquatic plants growing in them and were all positioned in full sunlight, so they were exposed to light for more than half the daytime hours.

Green water is more just an aesthetic problem rather than being due to the pond being unhealthy.  It is caused by microscopic algae floating around in the water. Algae grow when there is plenty of sunlight and are more prevalent in the spring through to summer months. The best solution is to provide shade for half to two- thirds of the pond. This can be achieved by planting floating aquatic plants.

Green water can also be treated by placing bales of barley straw in the pond until the water becomes clearer and less green.

One of the ponds had so much blanket weed you could hardly spot the gold fish swimming about. Blanket weed is a type of algae, consisting of long green threads, which float on the surface of the water. If it is not treated, it will start to kill the inhabitants of the pond. If you have this weed in your pond, place the handle of a rake in the pond and swirly it around gently to gather – up the algae. Keep repeating the process until you are satisfied that it has all been removed. Alternatively treat your pond with algaecide. This is harmless to plant and animal inhabitants, but the material left behind will provide nutrients for further algal growth so it is better to deal with what has caused this algae growth.

Algae apear in large masses if there are too many nutrients in the water. To avoid this happening in your pond, ensures that your fish only get the food they require and don’t over feed. Any left over food will place a burden on the ecosystem or natural balance of your pond.

Keep algae at bay by installing plenty of floating and underwater plants which deprive them of nutrients and light.

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