It isn’t sufficient to only test water that’s being added to the system. Even when the water is perfectly conditioned and balanced going in, the aquaponics system is full of factors that can push any quality measurement out of range within a matter of days. A proper testing routine is the only way to ensure water quality remains steady for rapid plant and fish growth.

Daily testing routines should involve measurements of the dissolved oxygen, nitrates, nitrites and ammonia levels. Simple vial or strip tests are available in bulk for all four of these, and tests for nitrates, nitrites and ammonia are often combined into one. All four of these water quality factors can change very rapidly. They are very destructive to both fish and plant roots, so they shouldn’t be assumed. At a minimum, they should be checked at least once every 24 hours.

Other water quality parameters are safe to test weekly, as they’re less likely to change rapidly. As long as the incoming water is tested routinely and comes from a stable source, factors like pH and suspended solids take days to weeks to change enough to affect your fish. Temperature measurements should be monitored constantly with the use of digital probes. Alarms should be set to go off when there’s a drop or spike, eliminating the need for daily or weekly readings.

Treating Water in Response to Test Results

Discovering a dangerously high nitrite level or unusual pH reading may make you feel like panicking, but water quality treatments require a calm and steady hand. Treating too aggressively, in an attempt to make a big change in quality, will only shock the system and increase the chances of fish and plant loss. Treatments should be done in graduated steps to ensure the adjustments occur slowly and are long-lasting. This prevents rapid swings in pH or nutrient levels.

Adjusting the pH

Adjustments to the hardness or softness of the water are best handled through a device known as a pH controller. This is a constant monitoring device that also dispenses the right amount of treatment to lower or raise pH as needed. It will maintain pH within the range you set. For a less high-tech solution, fine nylon mesh bags filled with the right treatment can be added to the filtration tanks to adjust the pH gradually. Aquaponics systems tend to become more acidic over time due to the nitrogen cycle that feeds the plants. So, you’ll need to add potassium hydroxide or calcium hydroxide in powder form to compensate unless you are adding alkaline water as a replenishment. Systems that are too alkaline will need treatment with phosphoric acid. Adding powders or liquids directly to the fish or plant tanks will damage the living components of the system, so always adjust the pH by making the addition in a filtration tank or a specific dosing container.

Controlling Ammonia and Nitrates

Because the conversion of ammonia to optimal forms of nitrogen is handled by bacteria, the primary treatment for high ammonia levels is to increase bacterial activity. Ammonia issues often go hand in hand with pH imbalances, as the bacteria also need a pH level above seven to function and stop entirely below this point. Using chlorinated water, even if there’s only the tiniest amount in the supply, also kills off bacteria and stops the nitrogen cycle. You may need to improve your filters or increase the amount of media bed space to boost nitrifying colonies.

Partial water changes are the best way to deal with nitrite and nitrate levels that have risen too high for the fish and plants. This indicates a system imbalance in which there are not enough plants to absorb the nutrients provided by the fish. Even though the bacteria are doing their work converting the waste into fertilizer, there’s simply too much fertilizer to go around. Reducing stocking and feeding rates, and increasing plant surface area, is the only permanent way to prevent these imbalances.

Increasing Dissolved Oxygen

The only two methods for increasing dissolved oxygen levels are to add more oxygen through aeration and to reduce the causes of oxygen loss. Direct sunlight, high water temperatures, algae, other water plant growth and overstocking of fish, can all lead to oxygen loss.