Algae has several undesirable effects in aquariums which have probably prompted you to go to great lengths 
(often pain staking) to achieve its successful control and treatment.
The most obvious effect of algae is the visual degradation of the appearance of your aquarium. The goal is to create an appealing environment with a high degree of clarity. Algal growth on glass, rocks, plants, equipment etc. challenges the achievement of that goal.
Less obvious, but more severe effects of algae is its negative impact on plants and fish life. A large number of algal blooms can lead to serious de-oxygenating which poses a significant threat to the well being of your fish.
Excessive algae growth will also crowd the environment in your aquarium and severely threaten plant life by competing for nutrients and blocking light.
Algae have a large diversity and some, mostly the unwanted, grow in environments with high nitrate and organic values. These conditions are especially preferred by the single celled members of cyanobacteria (blue green algae), diatoms (brown algae), dinoflagellates (brown slime algae) and members of the chlorophyta (green/hair algae).
All of the mentioned algae types can bloom (at a point where the population 
reaches large numbers, it will turn the water green) and cover most surfaces, leading to severe problems within the water environment.
Algae spores are readily available, just waiting for enough nutrients to break out. Nitrate levels above 10 ppm are sufficient to fuel their desire.
Algaecides based on antibiotics or chemicals will kill algae. However, they don’t work in the long run, because they leave the nutrients back, ready for new algae to grow. All of them have long term negative effects if used improperly or frequently.
Quick algae descriptions and algae treatment & control solutions:
Brown Slime Algae | Blue-Green Algae | Brown Algae | Hair Algae | Green Water
