As you may know, there are three essential nutrients you need to add to your aquaponics system. These are:
- Iron (Fe)
- Calcium (Ca)
- Potassium (K)
Calcium and Potassium will be in the mix that increases your pH.
Iron is one of the three elements that you need to supply to your aquaponics system. That’s why most aquaponics systems are iron deficient.
How to spot Iron deficiency
You can spot iron deficiency on the leaves of your plant.
If the leaves are turning yellow but the veins of the leaf is still green, you have iron deficiency. This phenomenon is called chlorosis.
Kale is a plant that will display signs of iron deficiency first. That’s why I recommend using kale as an indicator of iron deficiency in hobby systems.
If you have a bigger system or do commercial aquaponics, I highly recommend getting yourself an iron meter. You can check the levels of dissolved iron before deficiencies occur.
What kind of Iron do you need?
There are many types of iron, Chelated iron is the one that dissolved the best in your water.
I recommend using one that uses DTPA as . You can purchase chelated iron here.
The DTPA is a chemical compound that keeps the iron dissolved in the water. If there is no chemical compound, the iron would dissipate from the water.
Dosing Iron into your system
Iron levels in your system should be about 2.5 PPM.
The rate at which the plants take up the iron depends on what kind of plants you are growing.
Method 1: Dosing Iron every 3 weeks (without meter)
The UVI system, which used DWC troughs supplemented 2mg/liter every 3 weeks. 2mg per liter is the same as 2 PPM.
Most of the iron supplements are only a percentage of iron. The one I linked has 10% iron.
2 mg per liter means 20 mg per liter because it has only 10% iron.
20 mg per liter is the same as 75 mg per gallon of water.
Method 2: Dosing Iron going from measurements (Requires meter)
This method is more accurate but requires an iron meter.
You need to measure the current levels of iron in your system. You then need to apply the following formula:
Desired iron level – actual PPM reading = amount to be added (PPM)
Amount to be added (PPM) x (100/Percentage of iron in supplement) = mg/liter
100-gallon system with 1.9 PPM of iron measured. I use chelated iron at 10% DTPA.
2.5 PPM – 1.9 PPM = 0.6 PPM
0.6 PPM x (100/10) = 6 PPM or 6mg/liter
100 gallons = 378 liter.
378 x 6mg = 2268mg or 2.268 grams needs to be added to the system.
Iron deficiency occurs frequently in aquaponics systems. You can do three things:
- Wait for iron deficiency to occur and treat it
- Supplement iron periodically into your system
- Use an iron meter to check the iron levels of your water
Will my water turn red after I add Iron?
It depend on what kind you use. If you use Fe-EDDHA, your water will turn red. If you use the one I advised in the article, your water will not turn red because it’s DTPA .
Is iron OMRI (Organic Materials Review Institure) approved?
Most of them are not, but this one is.