Author: Aqua Gardening
Date: 27 December 2023

Chelated Iron for Aquaponics

Chelated Iron serves as a beneficial supplement in Aquaponics systems, effectively addressing iron deficiencies and promoting robust plant growth. Iron, integral to the plant’s overall metabolism, is indispensable for the synthesis of chlorophyll.

Iron plays a crucial role in plant growth, akin to potassium and calcium. However, fish food falls short in providing sufficient amounts of these nutrients for optimal plant development.

A clear indicator of iron deficiency in plants is the emergence of yellow leaves with green veins. The attached photo illustrates this deficiency in basil plants, where the yellowing of the leaves signifies a lack of iron.

Iron deficiency in basil leaves

The Best Chelated Iron Supplement for Aquaponics

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.

DTPA Iron Chelate Food Grade Powdered Nutrient
DTPA Iron Chelate Food Grade Powdered Nutrient

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.

Growth Technology Liquid Iron

Growth Technology Liquid Iron

 

Natural Iron Chelate from Home-made Fish Food?

Iron can be supplemented both organically and inorganically. Foods rich in iron such as liver, soybeans, lentils, spinach, chard, and kale can be incorporated into homemade fish food. To prepare this, blend these nutrient-dense vegetables into a fine, consistent puree using a high-speed blender. Once blended, freeze the puree and portion it out as needed 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.

edta dtpa addha iron chelate availability ph

Chart courtesy of https://www.akzonobel.com


How Much DTPA Chelated Iron does an Aquaponics System Need?

DTPA Iron Chelate Food Grade Powdered Nutrient

  • Use 10 grams per 1000L to raise iron chelate by 0.5ppm. Most systems will require 20 to 40 grams of DTPA chelated iron per month.

Growth Technology Liquid Iron

  • 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.