How to Control Pond Algae

Algae can be a headache for pond owners, especially when it blankets the surface of the pond, giving it an unpleasant appearance. Pond algae consists of mainly two types – the planktonic algae or the filamentous algae. Planktonic algae, otherwise known as single cell or pea soup algae, lends a green color to the pond water. Filamentous algae is hair-like in appearance and when in abundance, it can float over the pond like a green mat. Both of these algae, in small quantities, are beneficial to the environment of the pond, but can ruin the pond, if they grow unrestrained. Hence, it is very important to control the growth of algae in your pond in order to maintain a healthy atmosphere and preserve its beauty.

The uncontrolled growth of algae in a pond may be due to various reasons. The growth of algae depends on sunlight, sufficient nutrients like phosphate and nitrate and a higher pH level in the pond. The excess nutrients in the pond may be due to rotting vegetation, fish feed or dead fish, fertilizers from a nearby garden or lawn, etc. The rate of algae growth is higher in ponds in summers or when they get direct sunlight. The higher pH level of the water can be attributed to some materials used in the construction of the pond. Marble, limestone or concrete can alter the pH levels of the pond water. Lack of pond filters can result in stagnant water, which in turn becomes the perfect atmosphere for algae growth. Lack of healthy aquatic plants in the pond, can also lead to this menace. These plants feed on the excess nutrients in the pond, thus preventing algae growth.

Controlling pond algae can be started right from the construction of the pond. You can prevent the overgrowth and spread of the algae by various methods. Some of them are as follows:

• A slope made at the deepest point of the pond facilitates the collection of the debris in the bottom, which can be removed easily. A wall around the pond prevents the entry of run-off rainwater, which can increase the pH level of the pond water. Abstain from using limestone, marble or concrete in the construction of the pond. Algae growth is normal in newly-constructed ponds due to the high level of nutrients, so, wait for some weeks before adding fish. Fish can add to the nutrient content of the water. The pond should have a minimum depth of 24 inches, in order to prevent sunlight from reaching the bottom. You can design the pond accordingly, to reduce the overgrowth of algae.
• You can remove the algae manually or with the help of a pump or a soft brush. Add a variety of aquatic plants to consume the excess nutrients. These plants should cover 50 % to 70% of the surface area of the pond. Water lilies, water lettuce, water hyacinth are perfect to serve the purpose. You can also use submerged plants like anacharis.
• Another method to control the growth of algae is to add nitrifying bacteria to the pond water. This bacteria can feed on the nutrients, which are used by the algae for their growth. These bacteria can be grown on rocks, plants, etc. You can also add a bundle of barley straw to the pond. Barley straw helps keep the water clear and odor-free. You can keep the straw submerged in water, but don't allow it to sink to the bottom.
• Add some fish to the pond, which feed on algae. This can reduce the rate of algae growth in the pond to some extent. In such a case, you should not overfeed the fish. Reduce their feed, forcing them to feed on the algae.
• A pond aerator or a fountain can increase the oxygen level of the pond, thereby energizing the bacteria, which in turn helps in reducing the algae. These instruments can also help in a better circulation of water and lessen the growth of algae. Refrain from using tap water to clean the pond or for a water change. This can kill the beneficial bacteria too. Never go for a complete water change, which can result in a high rate of algae growth. Clean the bottom of the pond on a regular basis.

However, a pond does require algae in a moderate quantity, but never allow them to grow unrestrained. This can reduce the oxygen level of the pond, which in turn kills the fish too. Hence, controlling the growth of algae is important for a healthy ecosystem of the pond.