Cyanobacteria, also known as Blue-Green Algae, is a photosynthetic bacteria that can form a green carpet of “slimy” algae in your planted aquarium if conditions are right.   Cyanobacteria occur naturally in warm, calm lakes and waterways where there is an abundance of light and nutrients available.  Cyanobacteria is often blue-green in color, but can also be variations of blue, green and reddish-purple/brown.  In saltwater aquariums it is often found in its red-color form.   If left unchecked, Cyanobacteria blooms can happen quickly and will suffocate your aquatic plants, substrate, and hardscape materials.  Cyanobacteria is soft to the touch, and feels very slick and “goopy” when out of the water. 

Cyanobacteria occur in an aquarium when there is an excess nutrient load (nitrogen) and an abundance of light. Algae colonies, in general, grows at wavelengths between 660 to 700 nanometers. Cyanobacteria is known to grow at much shorter wavelengths between 530-620 nanometers.  Old bulbs and lamps will produce the lower wavelengths that will foster Cyanobacteria blooms.

Hobbyists may refer to Cyanobacteria as Blue-Green Algae (BGA) or Cyano for short.

Removal Tips

Antibotic Treatment

Antibotics are the best way to completely cure an aquarium of cyanobactera. A week treatment of products such as  Maracyn or erythromycin will cure the aquarium completely of this bacteria.

Manual Removal

Cyanobacteria is easy to remove by wiping it off leaves, aquarium glass, or other areas of infections.  Remove as much as you can during a waterchange, and remember to also clean out your aquarium filter.

Adjusting Photoperiod/Lighting Scheme

Cyanobacteria growth is a photosynthetic organism that is directly affected by the spectrum and intensity of your aquarium light source. Reducing the photoperiod, or turning off the aquarium light for a few days will disrupt Cyanobacteria growth. Replacing year-old bulbs will also help reduce reoccurring algae blooms. 

Nutrients and Circulation

Reduce nutrients dosed into the aquarium, and reduce the amount of fish food introduced to the aquarium.  Adjust filter water output, or add a powerhead to maximize circulation in the tank.


Cyanobacteria is prevented by introducing fast growing stem plants in the early months of the aquarium.  This will allow the aquarium to become balanced and established.  If you notice any Cyanobacterial bloom, remove it immediately and begin adjusting your lighting. Change any old light bulbs, and monitor nutrient loads to keep this algae from overtaking your planted aquarium.  

Algae Profile
Scientific Name: Cyanobacteria
Common Name: Cyanobacteria
Difficulty to Remove: Very Easy
Potential Causes: Nitrogen (N) Deficiency
Characteristics: Green Slime
Algae Removal Procedure: Balance Nutrients