The Key Elements of a Healthy Water Environment

By: Tawnya Sawyer

The Key Elements of a Healthy Water Environment

Water is THE lifeblood of your aquaponic system. It helps move the fish waste out of the tank into the filter and brings new fresh water to your fish. It recirculates nutrients from the filtration to the plants. Warm, nutrient-rich water provides the perfect environment for the bacteria to thrive and perform nitrification to keep the water safe for the fish. Properly aerated water allows the plant’s root system to flourish, so the plant can put energy into the leafy edible plant parts. And as an added benefit, water provides an extensive thermal mass for the greenhouse, mitigating temperature swings.

Since the fish, bacteria, and plants are ALL dependent on water, it is critical that you pay close attention and manage these four water qualities – Purity, Temperature, Aeration, and pH.

For successful aquaponics, it is important to learn how to manage the key elements of a healthy water environment.

The key elements include:

Purity – water that is safe and clean for the fish, bacteria, and plants.

  • Water that is safe for you to drink is still not ideal for sensitive fish, because it usually has chlorine or chloramine in it.
  • Water should come from a good source such as a well or municipal water.
  • Surface water (ponds, lakes, rivers, agriculture ditches, even rainwater) should be avoided since it is likely to have contaminants and harmful bacteria or pathogens that would be difficult to remove to keep your system safe.
  • Water should be filtered to remove contaminants, disinfectants, fluoride, heavy metals, prescription drugs and pathogens.

Temperature – Aquaponics works most effectively in temperatures between 68o – 75o F (20 o – 24o C.)

  • Water will naturally maintain the ambient temperature of where it’s located.
  • The type of fish you choose will dictate the optimal water temperature for your system.
  • If possible, select fish that will thrive at the water temperature of the system.
  • Remember, it is easier to heat water than it is to cool it, because there are more heating options.
  • Attract heat by using a dark colored tank, and retain heat through insulation.
  • Use a heater with a control unit that is sized appropriately for the amount of water being heated and the difference in the temperature.

Aeration – Fish, aerobic bacteria and plant’s roots all need oxygen in the water to be healthy and thrive. The greater the aeration, the greater the dissolved oxygen available for all living elements in the system.

  • Dissolved oxygen levels for fish must be above 3 ppm and preferably about 6 ppm.
  • It is difficult to have too much-dissolved oxygen in an aquaponics system.
  • Warm water holds less dissolved oxygen than colder water
  • Dissolved oxygen can be depleted very quickly if the power goes out or the aerator fails. This could cause significant gill damage to the fish if not death.

pH – The scale that represents acid, neutral or alkaline conditions in the water.

  • Ideal pH is between 6.8 – 7.5 in your aquaponics system. This is a compromise between the optimal ranges of the fish, plants, and bacteria.
  • Test pH at least weekly and as frequently as 3 – 4 times per week using an API Freshwater Master Test Kit.
  • During cycling, pH will tend to rise.
  • After cycling, the system’s pH will likely decline on a regular basis and need to be adjusted up (unless your water is very alkaline).
  • Buffer is your water’s natural tendency to return to a particular pH value.
  • pH can be adjusted up (more alkaline) or down (more acidic) depending on the hardness of your source water, the system buffer, the nitrification process and the needs of plants.

By following the Rules of Thumb for Healthy Water Environment, you are on your way to the successful management of your system. The keys are to start with relatively pure water, free of contaminants and pathogens. Then adjust it to the right temperature and make sure it is highly aerated.  The final step it to monitor the pH and adjust as necessary.