How to Identify Iron Deficiency in Aquaponics

Iron is one of the essential micronutrients necessary for plant development and fish growth in aquaponics systems. It is an important element for plant photosynthesis and many other cellular functions. With regards to fish, iron is an integral component of proteins involved in cellular respiration and oxygen transfer. 

Iron deficiency is common in aquaponics systems because of the low amounts of iron in commercial fish feeds. Therefore, iron supplementation is needed to ensure the optimal growth of plants. This article discusses different ways of supplementing iron and how to identify an iron deficiency in your aquaponics system. 

Why is Iron Important?

Iron is one of the essential elements on the planet. It is an important plant and animal nutrient vital to an aquaponics system.

  • Plants and iron

Iron serves many functions in plant growth. Iron is involved in the production of chlorophyll, which gives plants oxygen and its healthy green color. Without enough iron, plants cannot produce chlorophyll, which will cause retarded plant growth. Iron also plays an integral part in the plant's ability to process oxygen and carry it throughout plant cells from root to leaf tip. 

  • Animals and Iron

Humans and animals need iron to make hemoglobin, which helps bind and deliver oxygen to the body. 

How Iron Deficiency Affects Plants in Aquaponics

All plants will be at risk when an iron deficiency occurs in your aquaponics system. This is because, without the necessary levels of iron, chlorophyll production slows or stalls. The oxygen and other nutrients will be unavailable to other parts of the plant, which can cause stunted growth on leaves and stems, prevent seeds, flowers, and fruit growth and will damage the existing leaves. An iron deficiency in your aquaponics system may lead to plant loss or failure of the entire system. 


Plants Nutrient Deficiency Chart

How to Identify Iron Deficiency in Aquaponics Plants

The two ways of identifying an iron deficiency in your aquaponics plants are:

1. By Doing a Visual Test

Identifying an iron deficiency is generally straightforward. This is because once the levels of iron are low, plants will start to show various visual signs, which are:

  • Chlorosis or yellowing of the leaves that resemble a spidery weblike pattern on the leaves with the leaf veins remaining green.
  • Leaves may turn whitish before dying.
  • Stunted plant growth.

2. By Using Testing Kits Such as Iron Checker

Testing kits are also available to determine an iron deficiency in aquaponics systems. These testing kits will give you a clear indication of how much iron is available in the water. With these devices, you can easily read the amount of iron in water at ppm. When reading the result, remember that the ideal range is 2-3 ppm. A reading of 1.5 ppm showed an iron deficiency.


Iron Deficiency in Plants

How to Treat Iron Deficiency

In treating iron deficiency in your aquaponics system, it is essential to consider the severity of the deficiency, as this will affect the way that iron is added to the system. If the deficiency is severe and causing problems with plant health, it may be better to supplement iron by spraying it on the plant's leaves. This method will provide a more concentrated dose directly into the plant and can quickly help remedy the deficiency.

You can also choose to supplement the tank with iron.

Another thing to consider is the system's pH. A balanced pH can help your plants quickly recover from the effects of iron deficiency. A higher pH makes it difficult for the plant to absorb the available iron in the system.

There are many types of iron, but chelated iron is the one that works best in aquaponics systems because it dissolves easily in the water. When using chelated iron, you also need to know the difference between EDTA and DTPA. EDTA is a toxic version often used as a weed killer, while DTPA is an effective fertilizer and easily dissolves in the water. 

How Much Iron Do You Need to Add to Your Aquaponics System

Dr. Rakocy of the University of the Virgin Islands (UVI) created a standard dosing of 2 mg/liter of water and 7.58 mg/gal of pure iron every three weeks. You also need to check on the percentage of iron in the product you are using. If you use a product with 10% iron, you must add 76 mg of iron to every gallon of water every three weeks. 

Another method of dosing iron is going from the measurements of the iron meter. First, you need to measure the current iron level in your system and then apply the following formula: 

Desired iron level -actual ppm reading += amount of iron to added (ppm)

Amount of iron to be added (ppm) x (100.percentage of iron in supplement) = mg/liter


A system with 100 gallons has an iron measurement of 1.9 ppm. (I'm using chelated iron with 10% DTPA)

So, 2.5 ppm - 1.9 ppm = 0.6 ppm

0.6 ppm x (100/10) = 6 ppm or 6 mg/liter

100 gallons = 378 liter

378 x 6 mg = 2268 mg or 2.268 grams of iron need to be added to the system.

Preventing Iron Deficiency in Aquaponics Plants

Once the iron deficiency in your aquaponics system is addressed, you must take steps to prevent further issues. It is common for established systems to need additional iron from time to time, as both fish and plants need this nutrient for overall health and growth. 

To prevent the iron deficiency from happening again, you have to ensure to have a 10% chelated iron at hand at all times. Regular monitoring and water testing will ensure your system is balanced and healthy. For prevention, you can set a regular iron supplementation schedule, such as adding iron every two or three weeks. Checking your system's level will also ensure your plants will absorb the nutrients present in the system.


Plants need nutrients to grow healthy and thrive. So an aquaponics grower must be vigilant in preventing and treating any deficiency that may occur. Checking and testing the water regularly and ensuring the pH level is in its ideal range can help prevent any issues, so take time to monitor your system regularly. 


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