There are many factors that can cause green algae to appear in a garden pond. Too much sunlight, nutrient-laden water and your pond is invaded by a greenish aquatic mist. Once well installed, these algae tend to colonize the space, harming both the general balance and the aesthetics of the place. Let's see how to remedy it...
The causes of the invasion
Several causes are at the origin of the propagation of these green algae, but it is always due to an excess of nutrients in the pond water. The organic pollution of the environment is the result of several phenomena: too much food for the fish, plant debris that has fallen to the bottom of the pond for several months, fertilizer applied around the pond, or an overpopulation of fish in relation to the size of the pond are all aggravating factors.
Another cause is the lack of aquatic plants in the pond. After a harsh winter, some aquatic plants will have disappeared, others will take a long time to start up again, leaving green algae, which develop very quickly in the spring, to take advantage of all the nutrients present in the water. The aquatic plants will no longer be able to perform their filtration, depollution and shading roles, and the algae will have plenty of time to colonize the pond.
Note that constant sunlight can further aggravate the phenomenon. A pond should always be installed in semi-shade.
How to fight against green algae?
It is easy to prevent the appearance of green algae by following these few tips:
- First of all, make sure that you maintain your pond regularly. Plant debris (leaves, flowers, grass, etc.) that has fallen into the pond should be collected on the surface before disappearing to the bottom of the water, where it will decompose quickly. The same goes for aquatic plants, which should be cleaned of soft leaves and wilted flowers before they decompose in the water.
- Don't overfeed the fish; the right amount is the one that can be swallowed whole in a maximum of 5 minutes, otherwise it will all end up at the bottom of the pond.
- Another mistake to avoid is overcrowding the pond. Keep in mind that a goldfish will need 50 liters of water to be comfortable while a koi carp will need 1000 liters. These little creatures grow very fast, don't forget that!
- In the spring, as soon as all risk of freezing is eliminated, restart the filtration after a complete cleaning and a check of the filter. It is possible to inoculate the filter with biomass bacteria to increase its efficiency.
- Finally, check the condition of your aquatic plants and replace those that have not survived the winter. They have a major role of filtration and depollution in the pond. Plants that start their vegetative cycle very early in the season should be favored (Aponogeton, Elodea, Ranunculus, Sagittaria, Iris pseudacorus...)
- Install water lilies, water hyacinths and lotus if the depth of the pond allows it: their foliage will provide welcome shade to which you can add the planting of an evergreen tree at the edge of the pond.
