Chelated Iron for Aquaponics
Iron is an important nutrient for plant growth, but like potassium and calcium, fish food doesn't contain a enough to grow plants. Plants show iron deficiency by growing yellow leaves with green veins. The photo below shows basil plants with yellowing of the leaves which is a sign of an iron deficiency.
Chelated Iron is a supplement that can be added to Aquaponics systems to help fix iron deficiencies and to ensure the plants maintain healthy and vigorous growth. Iron has a number of important functions in the overall metabolism of the plant and is essential for the synthesis of chlorophyll.
The Best Chelated Iron Supplement for Aquaponic Systems
The best and most cost effective method of supplementing an Aquaponics systems with iron is by using DTPA Iron Chelate Food Grade Powdered Nutrient available from Aqua Gardening. Use 10 grams per 1000L to raise iron chelate by 0.5ppm. Most Aquaponic systems will require 20 to 40 grams of DTPA Iron Chelate per month.
Another good source of iron is Growth Technology Liquid Iron which supplements the three main types of chelated iron. It provides "available iron" to your Aquaponics system which is readily absorbed by iron deficient plants. It is a food-grade nutrient designed for hydroponics, but can also be used for Aquaponics at a reduced dose. Use 5ml of Liquid Iron per 100 litres to raise available iron by 0.5ppm, test and dose as required.
Natural Iron Chelate from Home-made Fish Food?
Iron can be supplemented organically and inorganically, just like potassium. Liver, soybeans, lentils, spinach, chard and kale are rich in iron and can be added to home-made fish food. To make your fish food, blend the vegetables using a high speed blender to get a consistent, fine puree. Freeze the puree and cut it out as required to feed the fish.
What About Other Types of Chelated Iron?
Not all types of iron found around your house or at the nursery are suitable for Aquaponics.
- The chelated iron found at hardware stores such as Bunnings is not recommended for use in Aquaponics systems. It is formulated for low pH soils, using a form of iron chelate called EDTA. A healthy Aquaponic system has a pH level between 6 and 7.5. EDTA Iron Chelate (Fe-EDTA) loses it's effectiveness on plants above a pH of 6. Basically it doesn't provide enough iron for plants when used in Aquaponics. DTPA Iron Chelate Food Grade Powdered Nutrient (FE-DTPA) on the other hand, is more effective in a pH range of up to 7.5 and is recommended for Aquaponic systems.
- Rusty pieces of iron or nails around your home are iron oxide, however in this form it isn't readily available for your plants if placed in your system.
- Another form of iron available in hydroponic products is Fe-EDDHA. This form of iron chelate is a deep purple colour and is extremely expensive, so it doesn't look great in your water or make Aquaponics cost effective.
Chart courtesy of https://www.akzonobel.com
How Much DTPA Chelated Iron does an Aquaponics System Need?
- Use 10 gram per 1000L to raise iron chelate by 0.5ppm. Most systems will require 20 to 40 grams of DTPA chelated iron per month.
- Use 5ml of Liquid Iron per 100 litres to raise available iron by 0.5ppm, test and dose as required.
How to Check the Iron Level in an Aquaponics System?
Instead of diagnosing iron deficiencies via your plant's leaves, the iron content can be checked within your system using an Iron Test Kit. The first test checks for available iron - this iron can be readily absorbed by your plants and will disappear quickly if you have alot of plants. The second test is for iron chelate - the amount of iron in the water which is broken down into available iron over time. We recommend keeping the iron chelate level in an Aquaponics system between 0.5 and 1.0ppm.