In Aquaponics, the water is recycled and used by the fish, plants and bacteria. In order for them to all live harmoniously together, there must be a common ground they can share. Several factors can affect the quality and livability of the water in an Aquaponics system. Factors such as temperature, salts, PH and oxygen all have to be maintained at the appropriate levels.
Since the water is shared, what may be optimum for one species may not be for another, so that they all must agree on the same thing. A PH of 7.0 is considered neutral and is the desired point in Aquaponic systems. During nitrification, bacteria create Nitric Acid, which will decrease the PH of the water. Adding some sort of base or alkaline will help buffer this acidifying effect and increase the PH of the solution. There are many brands of PH adjusting products, with a variety of ingredients for changing the PH. One product may use Phosphoric acid to decrease PH and another may use Nitric Acid.
For increasing the PH, Some use Potassium Hydroxide or Calcium Carbonate. Any time a PH adjuster is used, it adds additional properties to the water, depending on the ingredients. This can be a desired effect if needing additional nutrients for the system such as Potassium for plant development. Due to the acidifying effect of the bacterial conversion, raising the PH is the most common issue in Aquaponics water quality. Some employ a slow release method of PH buffer such as Dolomite lime or crushed seas coral that adds carbonate slowly to the water as it degrades.
Sudden changes in PH can lead to fish and bacteria mortality due to stress. Plants are a little more resilient, but at extreme ranges, will be unable to take up nutrients and can lead to further imbalance of the system. Temperature is another factor that needs to be regulated. When systems are located outdoors, they are exposed to weather extremes that can cause parameter shifts that can lead to system failure. Being able to control your environment can greatly increase your chances of a successful system.