Pond Algae is a loose term that describes the different species of algae, commonly found in fish ponds. Some forms of algae are of benefit to the pond system whereas others can be considered to be more of nuisance. It is important to prevent algae blooms if you want to keep your Koi and other pond fish alive.
Common Pond Algae Types
The most common variety is the suspended or floating green algae, such as Chlamydomonas, Chlorella and Euglena species. These microscopic unicellular organisms grow to about 4 microns in diameter (4 millionths of a meter). They multiply rapidly by means of spores, cell division or fragmentation. These green algae varieties are sometimes known as pea soup algae because they will in extremely high numbers turn your pond into something that resembles a bowl of pea soup.
Filamentous string algae look like long green hair and have a thread like appearance, due to a series of cells joined end to end. Horsehair algae, also known as Pithophora and blanket weed varieties such as Cladophora, Oedogonium and Spirogyra are particularly common.
What Causes Pond Algae To Grow?
The three factors that allow pond algae to develop are clear pond water that allows sunlight to penetrate, nutrient rich pond water and heat. An increase in temperature accelerates both suspended green algae and blanket weed growth.
How Do The Various Pond Algae Types Affect My Pond?
Suspended planktonic algae multiply at a rapid rate and can only really be controlled by ultra violet light from a UV sterilizer or UV clarifier. The UV light breaks the cell walls, causing the algae to clump together. As they stick together the mass becomes bigger, making it possible for it to be filtered out by a biofilter. Excessive suspended green algae form what is known as algae blooms. They can be catastrophic to pond fish populations as they will eventually starve the pond of oxygen, particularly in hot temperatures, where atmospheric oxygen can not be absorbed into the pond as easily.
Blanket weed and string algae varieties, multiply rapidly and form long, slimy clumps that attach themselves to any available surface. They consume large quantities of nutrients and will tend to be a dominant species. Once blanket weed forms in your pond it is almost impossible to get rid of.
Why Is Excessive Pond Algae Bad For Garden Ponds?
* It not only makes the pond look untidy and over grown but can in worst case scenarios actually cause the pond to smell.
* As algae blooms and filamentous string algae die they start to decay on the pond floor, where they give off carbon dioxide. The increase in carbon dioxide acts as a food source for the remaining algae, starting the process off all over again.
* The decaying process consumes oxygen from the pond water. This is particularly bad for the nitrifying bacteria and pond fish species, which need oxygen to survive. Remember that ammonia needs to be converted into nitrites and then into nitrates by the nitrifying bacteria. The oxidization process requires vast quantities of oxygen in order to occur.
* The increase in ammonia, which is also produced by rotting algae matter, places additional strain on the pond filter that houses the nitrifying bacteria.
Methods commonly used To Control Pond Algae
* The most successful and in my opinion the only really effective method of controlling floating planktonic algae is to use a UV sterilizer or UV clarifier. The ultraviolet light bombards the single celled algae, causing it to die and stick to other dead algal cells.
* Try where ever possible to remove as many of the nutrients from the pond as possible. Nutrients, mainly in the form of nitrate and phosphorous act as a food source for the pond algae. A good habit to get into is to remove excess fish food after feeding and to remove floating surface debris with a pond net. When feeding pond fish it is better to feed little and often, so as to prevent waste.
* Try to cover at least one third of the surface area of the pond with pond plants, as they compete with algal cells for the available nutrients in the pond water.
* Perform routine cleaning by removing blanket weed and string algae with a rake.
* The use of barley straw products will help to inhibit the algae growth. Barley straw bales are best placed in the pond in early spring, where the natural decomposition releases chemicals in preparation for summer when nutrients and sunlight are at their peak.
* The Centre for Aquatic Plant Management has discovered that ultrasound waves are proving to be one of the best solutions in the fight against blanket weed. The ultrasound breaks down the cell walls, causing death within 3 weeks. This is at present an expensive treatment and requires specialist installation.
* The use of pond algaecide treatments is common practice, but is in my opinion not a good idea. These chemicals can cause harm to pond fish, nitrifying bacteria and pond plants, if over dosed.
To conclude I would like to add that some pond algae is beneficial to the pond, as it provides a source of food for fish, provides shade from the hot sun and provides a hiding place from heron, king fishers and other predatory birds. It is natural to have some algae growth on pond surfaces, pond filters, pond pumps and other pond keeping equipment. The secret is to keep it under control.
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