Green water is a form of algae that can grow in your pond and only needs light, water and nutrients in order to survive. The more these elements are available to the microscopic algae, in the form of sunlight, biological matter and pond water, the quicker the algae will grow. Green water can lead to serious health problems for fish and aquatic life as well as making your pond look less attractive.
Fortunately, green water is an extremely common problem and therefore is easily treatable.
The most common cause for green water is an over-abundance of either sunlight or nutrients in the pond. Nutrients can count as anything on which the algae can feed and spread. The most common of these nutrients include phosphate, nitrate, nitrite and ammonia.
Green water is especially common during the summer because the algae tends to see large amount of light, therefore rapidly speeding up its growth and risking the pond starving of oxygen.
For fish, green water dramatically effects the levels of oxygen within the water and literally starves the fish of oxygen, which is especially dangerous for ponds which keep larger fish, as they require larger amounts of oxygen.
There are several ways to overcome and help treat as well as prevent the build-up of green water.
One of the most natural ways to fight green water is by introducing plant life to the pond. This will help by using and therefore balancing the nutrients present in the water. Pond plants can also provide shade, thereby limiting the amount of light being provided to the green water.
An alternative would be to install a UV clarifier. UV clarifiers usually come as part of a filtration system. As the pond water is exposed to the UV clarifier, the algae cells will be killed and therefore be unable to spread. As well as eradicating the initial problem of green water, using a well maintained and designed UV clarifier in your pond permanently will help keep green water at bay.
Other methods include algicides which are chemicals that kill the algae, for example a herbicide. However, these are often short-term fixes that don’t address the initial cause of the algae. Chemical filter media like phosphate removers can help to prevent or starve green water by removing their nutrients from the water.