Algae is naturally occurring and should be present in reasonable amounts in any healthy aquatic ecosystem. However in excessive amounts, it is definitely an aesthetic problem which needs to be brought under control.
The first key to controlling algae is to limit its nutrient source, specifically fertilizers in the water.
With a fish pond, fish waste is the primary source of nutrients for the algae. Thus, step one, if you have not done so already, is to stop feeding your fish, at least until you get the algae under control. The fish will eat the algae and can live for months off it and other organic material in the pond, such as insect larvae.
Another method to limit nutrients, is to have plenty of aquatic plants which grow rapidly and thus assimilate the nutrients. They are basically out competing the algae for available nutrients. Examples of rapidly growing aquatic plants include water celery, water hyacinth, umbrella palm, and water mint.
Ideally the pond water should circulate through the roots of the aquatic plants, enabling them to efficiently absorb the nutrients. This can be achieved by planting the plants in a gravel bed through which the water is circulated. Floating plants such as water hyacinth just need to be positioned so that the water flows past their roots. A successful plant filter will need to be pruned or thinned as it grows so that it does not take over the pond.
Algae also needs sunlight, so limiting sunlight will help. The lily pads of water lilies are also beneficial. Shade trees help, but may not be a quick solution. A black dye which limits sunlight penetration is available, but it also limits visibility of any fish.
Another element in algae control is a biological clarifier. Its function is to break down organic wastes and thus speed their removal from the pond. Strong aeration is also good as it speeds up waste decomposition and removal.
Barley straw is an old method just rediscovered. It acts by releasing chemicals into the water which inhibit algae growth. Unfortunately, it takes about a month to begin working. There are also some who believe that as algae dies it releases chemicals which inhibit further algae growth. Thus many algae blooms are self limiting.
In other words, it may be best to endure a current algae bloom. When doing that, be sure to have vigorous oxygenation, because dying algae consumes a great deal of oxygen, which can lead to your fish dying from a lack of oxygen.
All the above methods of control are natural and completely harmless to birds and fish. We have found that they are simple, effective, and low maintenance, particularly when compared to elaborate filters which require frequent cleaning, or UV sterilizers which are costly and complex.
Copyright ©2003 Avian Aquatics Used With Permission
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