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Aquaponics System Biology

SCOPE: To discover the important parameters and better understand the role of natural processes in an Aquaponic System.

Aquaponics System Biology…1

We understand that in Aquaponics system produces fish and plants together in one symbiotic system, and we now know that there are two major bacteria that convert the primary waste of the fish, Ammonia to Nitrates, that is, plant food.

Just to recap on those two Bacteria families are …
1. Nitrosomonas bacteria
2. Nitrobacter bacteria
Bacteria of various types is all around us and in our own bodies. There are simply millions of different bacteria. In nature bacteria perform many complex tasks taking one compound and by extracting energy from it for themselves convert it to another compound. These two bacteria groups listed above are particularly important to our needs and given the right conditions will work for us around the clock.

Bacteria needs a food source, water, and be housed within a temperature and pH range conducive to their happy survival.


  • The temperature for optimum growth of nitrifying bacteria is between 77-86° F (25-30°C).
  • Growth rate is decreased by 50% at 64° F (18° C).
  • Growth rate is decreased by 75% at 46-50° F. (8 to 10 C)
  • 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) (1)

Nitrobacter bacteria is less tolerant of low temperatures than Nitrosomonas bacteria. In Aquaponics systems, care must be taken to monitor the accumulation of nitrites especially when there is a change in water temperature of the system.

pH range

  • The optimum pH range for Nitrosomonas is between 7.8-8.0.
  • The optimum pH range for Nitrobacter is between 7.3-7.5

Nitrobacter will grow more slowly at the high pH levels . At high pH Nitrosomonas will grow more slowly and increases in ammonia may become evident. On the low end Nitrosomonas growth is inhibited at a pH of 6.5. All nitrification is inhibited if the pH drops to 6.0 or less.

Care must be taken to monitor ammonia if the pH begins to drop close to 6.5 as it may not be being processed as quickly as it is at higher pH levels.
This information has been taken from standard texts on the subject and we have observed that the tolerance range is most likely wider than most texts suggest. (2)

Beneficial Bacteria have four main benefits for areas like fish intestine lining and plant root tissue.

  • Beneficial bacteria help the balance of a system by: (Fungi help as well but that is another discussion)
  • Preventing harmful bacteria from taking hold. If the system is already occupied by a beneficial bacteria then the harmful bacteria has difficulty in taking hold. The microbes make Aquaculture and Aquaponics possible.
  • Promoting system health. Beneficial bacteria play an integral part in breakdown of organic material and actively assist plant and fish tissue health.
  • Being antagonistic to harmful bacteria. Beneficial bacteria inhibit harmful bacteria taking hold. By actively antagonising harmful bacteria the harmful bacteria are held in check in the Aquaponics system.
  • Improving nutrient uptake and general system health.

Aquaponics Microbes:-
It is most important to understand that many more things other than just the two bacteria groups discussed above. Many more are at work in the natural ECO system that we have pulled together in building an Aquaponics system. Fungi, algae, zooplankton, phytoplankton, protozoa, nematodes, just to list some. All of these microbes are the “work horses” of the system. Bacteria process the fish wastes into products that are non-toxic to the fish and make these products available to the plants as food.

Learn more about the actual numbers and parameters by attending the Practical Aquaponics Master Class

(1) Nitrifying Bacteria Facts - Bio-Con Labs. (n.d.).
Retrieved from http://bioconlabs.com/nitribactfacts.html

(2) Bhaskar Vijaya , E?ect of environmental factors on nitrifying bacteria isolated from the rhizosphere of Setaria italica : Department of Microbiology, Sri Krishnadevaraya University, Anantapur 515003, AP, India. 2005.

Posted By Murray Hallam on 30th July 2014

Updated : 21st November 2014 | Words : 669 | Views : 3215

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Murray Hallam is probably the best-known face in the world-wide Aquaponics movement. Murray is by nature an innovator and in his Research & Development facility has perfected many new methodologies for commercial farm Aquaponic systems.


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