Controlling Algae

There are various forms of algae that grow in a water garden, and when kept under control, some algae is desirable because it acts as a water purifier and a home to necessary micro-organisms. A well-balanced water garden has a thin layer of algae on everything that is under water.

You can control algae several ways:

chemically;

through filtration;

using bacterial inoculation;
or

by establishing a balance in the pond between plants and fish.

Many gardeners use a combination, such as creating a natural balance aided by filters and bacteria.

A natural balance is created by planting. Plants with floating leaves, such as water lilies, are most important because they reduce the penetration of sunlight into the pond, keeping the water at a cooler, more constant temperature. Try to cover 50 to 75 percent of the surface with plants with floating leaves. Submerged plants, such as Anacharis and Cabomba (oxygenating grasses), are functional and vital to establishing an ecological balance by absorbing nutrients from the water that otherwise would be fed on by algae. Scavengers, such as snails, mussels, and tadpoles, are essential because they consume organic wastes that settle to the bottom of the pond, they graze on the sides and surfaces of the pond, and they consume suspended algae in the water. Most people choose to add fish, such as goldfish and Koi, for their ornamental and aesthetic value.

There are bacteria that help control algae by consuming the nitrogen in the water garden. Once such a bacteria is established, the water should be clear except for a thin layer of algae on submerged surfaces that will house the beneficial bacteria

Filtration is the most common way to keep algae out of the water garden. The filtering process removes suspended particles and helps to oxygenate the water. Biological filters use bacteria to convert waste into usable forms of nitrogen for processing by aquatic plants. Most biological filters have a mechanical and biological chamber for the most effective algae control.

There are chemical controls (algaecides) available to control algae, but these should be considered only as a temporary measure to control algae that is already out of hand and preferably used as a last resort only. The algaecide should be applied according to label directions, with careful attention paid to impact on or the need for temporary removal of any fish in the pond.

Remember, algae control takes time -- several weeks may be necessary to achieve a natural balance in your water garden.