Your plants need Nitrogen to grow. Nitrogen comes in many forms – Ammonia, Nitrite, and Nitrate. We need to know how much Nitrogen is in our Aquaponics system. We could perform a persulfate digestion to get TN (Total Nitrogen), but in a properly running Aquaponics system, the majority of Nitrogen will be in the form of Nitrate.
When setting up a new system, or making major changes (such as a grow bed cleaning, adding new fish, or changing feed rates) I recommend testing Ammonia and Nitrite as well as Nitrate.
The Nitrogen Cycle
In the nitrogen cycle, bacteria break down the nitrogenous compounds (fish waste & uneaten food). First, Ammonia is changed into Nitrite. Then, Nitrite is changed into Nitrate. Both Ammonia and Nitrite are dangerous to fish, but Nitrate is fairly well tolerated by most species.
Testing for Nitrate in Aquaponics
- API Nitrate Test (0, 5, 10, 20, 40, 80, 160 ppm) $8.92 / 90 = $0.10 per test.
- LaMotte Smart3 + 3689-SC. Zinc Reduction. (0.0-60.0 ppm) $33/50 tests = $0.66 per test.
- Hach DR900 + 8039 Nitraver 5 Cadmium Reduction. (0.3 – 30pppm) $50.39 / 100 tests = $0.54 per test
- YSI 9500 + NitraTest. (0.0 – 20.0 ppm) $155/200 = $0.77 per test OR $60/50 = $1.20 per test