If conditions are optimal, algae will grow in lakes and ponds. In fact, algae grows in most lakes and ponds, but usually does not reach harmful levels. There have been over 30,000 types of algae discovered, and remarkably, some have been around for at least two billion years (source).
Algae are plants and exist in three forms. Most lack the various parts that make up typical plants, like roots, stems, or foliage. Planktonic algae are single-celled and free-float suspended in the water. They are the ones that cause the most headaches for pond owners. Water has an unpleasant odor and taste as a result of their presence. How it gets to your pond is somewhat amazing. It can survive the water purification system and only one spore is necessary to start a colony. Most are killed by the water company’s filtration process, but not all.
Filamentous algae, and Spirogyra (less common), are thread-like and make suspended mats on the pond bottom and the sides of rocks. Some mat on the lake surface. This type of Spirogyra algae is less likely to form high density blooms.
Many Macrophytic algae are affixed to the lake or sea bottom and have leaf and stem-like form. They appear similar, but have nothing in common anatomically with the complex land dwelling plants. Many seaweed, a loose term describing some benthic marine algae, are red algae, brown algae or green algae. Some seaweed are an example of plants belonging to the polyphyletic group of multicellular algae, meaning, they do not share a common ancestor (source).
Algae creates problems for other aquatic life when it covers a lake or pond, like depleting oxygen levels, blocking sunlight and nutrient reduction. Fast growing algae gobbles up nutrients rapidly.
Algae has benefits for some creatures by providing a food source.
They provide food for most marine base chains, and without algae, the waters would not sustain life.
Most algae accumulation is the result of surface runoff of surrounding areas, dumping nutrients like nitrogen and phosphorus into the water. An algae bloom can also occur as a result of changing water currents which stirs up the bottom and allows nutrients to rise to within the sunlight reaching surface.
When algae is floating on the surface, mechanical removal by raking is the best ecological alternative. Herbicides can be applied, but they can be harmful to aquatic life. Grass carp eat algae and have been used to control ponds.
Algae As Renewable Energy is a good idea!
“Algae biomass from lakes and ponds can now be used for energy with the advanced technology of Algae Aviation Fuel. Their method can transform any fresh water blue-green algae into a viable turbine bio fuel for use as generator ground electrical power. This modern technology is a first of its kind that does not require the extraction of oil from algal biomass to make fuel. Countries all over the globe with algae bloom problems can now harvest the biomass for use as energy instead of land filling the biomass or using herbicides.” (source)
If you want additional information on algae, click the three links. The first link is by Natural Environmental Systems and they offer natural control methods. Don’t let your Koi pond get looking like these examples. Koi will eat algae, but if levels are high, it is dangerous for the Koi for the reasons explained above.