from the blog

Take Good Care of Nitrifying Bacteria in the Aquarium

Care and maintenance

September 26, 2020

By Robert Paul Hudson

Did you know there are ways to promote the growth of healthy nitrifying bacteria in the aquarium and things to avoid which will adversely affect bacteria?

There are many strains of the nitrifying bacteria species and each may have varying tolerances, but in general, the following information applies to all of them:


Temperature plays a role in the growth rate of bacteria.

  • 77-86° F (25-30° C)  is the temperature for optimum growth of nitrifying bacteria
  • At 64° F (18° C) the growth rate is decreased by 50%
  • At 46-50° F. Growth rate is decreased by 75%
  • No activity will occur at 39° F (4° C)
  • Nitrifying bacteria will die at 32° F (0° C).
  • Nitrifying bacteria will die at 120° F (49° C)

In cold water systems, careful attention should be given to monitor the levels of nitrite.


The optimum pH range for Nitrosomonas is between 7.8-8.0, and for Nitrobacter is between 7.3-7.5. Below these ranges growth is slowed down. All nitrification ceases at a pH of 6.0 or lower. Ammonia levels should be closely monitored at a pH of 6.5 or lower.

Dissolved Oxygen

Oxygen levels have a direct effect on nitrifying bacteria. At very low levels the bacteria basically become inactive.  The bacteria reach their highest level of nitrification when dissolved oxygen levels reach 80% saturation.


Just like plant life, bacteria need nutrients to feed on for energy and growth. Many micronutrients are used by bacteria including phosphorus which plays an important role in the conversion of ATP to energy for cellular functions. Phosphorus is usually present in the form of phosphate in tap water and from decaying fish foods or other decaying organic material, but if your aquarium has no measurable level of phosphate it would be a good idea to introduce a small amount by way of phosphoric acid, mono-sodium phosphate or di-sodium phosphate.

Other micronutrients, (minerals) are normally found in ample levels in tap water. RO, deionized, or distilled water that is completely stripped of all minerals is inhibitory to nitrifying bacteria. It is important if using this type of water to replenish the water with mineral salts for the overall health of the aquatic system.

You can use products like the EcoBio-Block line, which contain special beneficial bacteria (bacillus subtilis natto) that are already packaged with the micronutrients they need to keep levels of good bacteria high and cloudy water and odor non-existent. These bacterium can survive from the strong acid of pH 3 to the strong alkali of pH 11, and are active in temperatures from 50° F to 149° F.

Nitrifying bacteria play an important role in keeping a healthy and balanced aquarium, but are also dependent on a balanced environment in order to function and grow- as all life is.