Algae are microscopic plants which grow in the water. Algae like all plants get their energy from photosynthesis. They absorb nutrients from the water and prepare food in the presence of sunlight. Algae play a beneficial role in the aquarium. The serve as food for many species of fish. They also help lower the nitrate level in the aquarium.
However, sometimes if there is too much light or too much of nutrients in the water. The algae population can explode. This can result in algae colonizing the aquarium tank walls and affecting visibility.
The water can turn green due to the algae. Algae can also colonize the equipment fitted in the aquarium such as filters and other decorations.
Algae Bloom can be prevented by cutting off light and nutrients.
Do not leave the lights in the aquarium switched on for extended periods. Ensure that partial water changes are carried out periodically. This will ensure that excess nutrients are not available.
Having live plants in the aquarium also reduces the algae population. This is because live plants compete with algae for the same nutrients. The nutrient levels are thus within limits.
Ultra Violet Sterilizers which sterilize the water using an ultraviolet heat source can also be used to keep the algae population in check.
There are also special algicides which can be added to the water to control algae.