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Cyanobacteria in the Reef Tank

Gram-Negative Photosynthetic Bacteria

"Red slime algae" or "cyano" is common in our reef tanks. While it is present in every aquatic environment, this bacteria only presents itself to the eye when conditions in its' environment allow it to populate quickly forming a buildup of the bacteria's waste that we see as red, tan, green, blue and sometimes black fuzzy or matted slime on the surfaces of rock, glass, and sand. We avoid chemical treatments and choose to treat naturally at our facility allowing the ecosystem to balance while also looking for the source or change in conditions that caused the bloom.


Possible Causes and Treatments


  1. Imbalance of nitrates and phosphates ~                                                                                                                                Test Nitrates and Phosphates, whether high or low nutrients these two parameters just need to be in a balanced 1:100 ratio (see Testing your Tank for our goal parameters) While we run low nutrients in our systems, we see very successful systems run on very high nutrients and as long as these two are balanced it keeps cyano from being able to outcompete beneficial bacteria.                                                                                                                                                                         

  2. Lack of beneficial bacteria and microorganisms~                                                                                                                   Add beneficial microorganisms such as bacteria, phytoplankton, copepods, stomatella and elephant snails, microbrittle stars and other animals that consume or outcompete the cyanobacteria. Injecting Bacteria directly into the sandbed can be very helpful.                                                                                                                                                                                  

  3. Warm temperatures and low flow where detritus and debris can buildup~                                                                         Turn tanks temperature to 76 Degrees Fahrenheit and increase flow in areas of buildup                                                          

  4. Low quality food or additives ~                                                                                                                                                Cut back, reduce or stop dosing amino acid additives, trace elements and other quick chemical fixes that can alter the balance of your ecosystem.                                                                                                                                                            

  5. Water Source ~                                                                                                                                                                     Avoid using tap water and/or check RODI filters. If filters haven't been changed silicates can build up creating favorable conditions for cyano.                                                                                                                                                 

Helpful Tips:

​ Gravel Vac places where buildup occurs. If nutrients are low you can gravel vac into a filter sock and put the filtered tank water back into the tank to reduce the amount of change to the environment. 

Keeping a schedule for the tank and keeping your routine consistent will help with balance and stability. 

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