It is unsightly and can become a menace if not controlled. In extreme instances, algae can grow until it suffocates your plants and fish, and completely fills a pond. However, there are reasons this occurs and plenty of precautionary measures that can be taken to prevent such uncontrolled growth.
Algae thrive for the same reason the plants in your garden thrive. They need a light source available, nutrients to feed on, and water. Without any one of these three present, algae will not be able to grow.
In order to control algae in your pond, you will need to control one or all of these factors. We will obviously ignore the water factor, since we do not have a pond at all if we do not have water. That leaves us with light and nutrients as elements we can control.
To reduce the nutrients in your pond that is causing your algae to thrive, you first need to clean your pond. Get rid of any dead and decaying leaves on the bottom or along the sides of the pond.
The next way to get rid of the nutrients in your pond is by adding beneficial bacteria to your pond.
Beneficial bacteria is required to not only break down toxic ammonia from fish wastes into harmless nitrates (referred to as the Nitrogen Cycle) but also to consume the same nutrients as algae does. When you add more beneficial bacteria, you starve out the algae, thus resulting in a clearer pond!