Combating algae in your garden pond

If the water in your garden pond is looking increasingly murky, this is most likely due to algae. You need to act quickly to protect both the water quality and the pond life.

Every garden pond has algae. Alight green shimmer on the surface of your pond is no reason for concern, providing the water remains clear on the whole. This effect is usually caused by green or blue algae (which are not actually algae at all). Green algae is a welcome food source for water fleas. It is partly thanks to these hungry little helpers that the pond’s biological equilibrium is maintained.

Algae infestations in garden ponds are usually caused by much larger filamentous algae. This algae can be identified by its long, thin filaments. It grows on stones or floats on the surface of the water like cotton wool, and multiplies very quickly given the right conditions.

It cannot thrive while the concentration of nutrients in the water is relatively low. In the summer, however, once the phosphate and nitrate levels increase, the sun becomes more intense and the water temperature rises, conditions are perfect for the algae and it can quickly take over. Following this “algal bloom”, the water can become unbalanced as the pond lacks oxygen and the pH value becomes too high. A short algal bloom occurs in almost every pond in the early summer. But if it does not disappear of its own accord, it can pose a threat to both the water quality and the pond life. As the pond owner, you must act quickly and systematically.

Preventing algae
What exactly can you do to prevent an infestation of algae in the first place, or combat an acute case quickly? First, it is vital that you keep the nutrient levels low or reduce them as necessary. As plants retain nutrients, the best preventive measure we can recommend is to stock your pond with plenty of plants in the spring. But make sure that you cut them back heavily on a regular basis, otherwise the nutrients will return to the water as the dead leaves and flowers decompose. If the plants are not sufficient and the increasing temperatures result in an acute outbreak of algae, you can use a phosphate binder to quickly “fish out” the nutrients. However, this is not a long-term solution. You must, therefore, also combat the cause of the excess nutrients.

A simple and particularly effective way to combat algae is to remove the pest from the pond by hand and to clean the water thoroughly using a dip net. This will not only remove the filamentous algae but also some of the surplus nutrients as you fish out the dead leaves, excess fish food and fish excrement.

A filter system for your garden pond
You can also use a filter system to help regulate your pond. You will need one of these filters anyway if you keep large fish such as koi. You can also help to prevent the build-up of nutrients by using a pond sludge cleaner. However, pond sludge should only be tackled in the spring, and should never be removed completely. A tool known as a skimmer can be used to filter the water on the surface and ensure that there are no dead leaves floating around.

Make sure that no lawn fertilisers find their way into the water as this would introduce additional nutrients to the pond. You should also refrain from using calciferous stones for decoration and allow nature to lend a helping hand by introducing native carp families and rudds to your pond. These fish are particularly partial to filamentous algae.

Call into your local store today to discuss your fish’s personal needs with our Maxi Zoo Pet Experts.

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