3.7 CHAPTER SUMMARY

• Water is the life-blood of an aquaponic system. It is the medium through which plants receive their nutrients and the fish receive their oxygen. It is very important to understand water quality and basic water chemistry in order to properly manage aquaponics.

There are five key water quality parameters for aquaponics: dissolved oxygen (DO), pH, water temperature, total nitrogen concentrations and hardness (KH). Knowing the effects of each parameter on fish, plants and bacteria is crucial.

• Compromises are made for some water quality parameters to meet the needs of each organism in aquaponics.

The target ranges for each parameter are as follows:

PH 6-7
Water temperature 18-30 °C
DO 5-8 mg/litre
Ammonia 0 mg/litre
Nitrite 0 mg/litre
Nitrate 5-150 mg/litre
?? 60-140 mg/litre

 

 

There are simple ways to adjust pH. Bases, and less often acids, can be added in small amounts to the water in order to increase or lower the pH, respectively. Acids and bases should always be added slowly, deliberately and carefully. Rainwater can be alternatively used to let the system naturally lower the pH through nitrifying bacteria consuming the system's alkalinity. Calcium carbonate from limestone, seashells or egg shells increases KH and buffers pH against the natural acidification.
Some aspects of the water quality and water chemistry knowledge needed for aquaponics can be complicated, in particular the relationship between pH and hardness, but basic water tests are used to simplify water quality management. Water testing is essential to maintaining good water quality in the system. Test and record the following water quality parameters each week: pH, water temperature, nitrate and carbonate hardness. Ammonia and nitrite tests should be used especially at system start-up and if abnormal fish mortality raises toxicity
concerns.