Besides amonia-nitrate, pH & temperature are the two most important parameters that should be tested regularly


Testing pH in an Aquaponic System

An aquaponic systems needs to find a compromise between optimal pH requirements of the fish plants and bacteria because all are somewhat different. The optimal pH for fish, plants and bacteria are:

  • fish- 6.5 – 8.0,
  • plants- 4.5 – 7.0,
  • bacteria- 6.0 – 8.0.

Therefore, the best pH to aim for in your aquaponic system is between 6.7 to 7.0 pH.  This compromise is good for the fish. It makes sure the ammonia is low and ammonium high. Refer to the diagram below. This compromise in pH is also good for the for the plants. It’s in a range that their needed nutrients are mostly available. Lastly, it is good for the bacteria. You can test the pH with an inexpensive pH test kit from an aquarium store. The brand I find most accurate and convenient is the API Freshwater Kits, using liquid drops in the test tube they provide. There are more sophisticated pH meters. If your in it for “keeps”, you should make the investment. Hanna is a well known brand. A Hanna Como pH-ppm meter is standard equipment for me. They have Nitrate-Amonia meters as well.

Testing Temperature in an Aquaponic System

Plants have a wide range of temperature tolerance. But it is best to monitor temperature ranges for the health of your fish as well as your beneficial microorganisms in your growing media. Different fish will have different optimal temperature ranges. For example Talapia aurenus has a wide range it can survive in (8′ to 30’C), however 20 to 24’C is optimal. You need to be familiar with your particular fishes optimal range.

Fish could have digestive problems at temperatures above or below their optimal range. But another very important factor concerning water temp is the pH.  With water temperatures outside the optimal range, the bacteria which covert your ammonia into usable Nitrate will loose efficiency  and slow in this nitrogen conversion. The fish may then be subject to dangerously high ammonia levels that are toxic to the fish.