Iron in Aquaponics

October 07, 2021

Should you be supplementing your system with iron? If so, how often? Or how much iron? Why is it so important anyway? We understand you may have a few questions regarding iron in aquaponics and we thought it would be a good idea to answer as many as possible in one blog post! So, let’s dive in and look at the importance of iron in aquaponics.

Why is iron important?

Iron is an important macronutrient that is required by living things, both plants and fish alike. Therefore, we need to ensure that our aquaponics system has enough iron to support the intake requirements of all living components in our system. Iron is essential as it assists in DNA synthesis, photosynthesis and many general cellular functions in plants. However, your fish also require a certain amount of iron to assist with oxygen transfer and cellular respiration. Moreover, if you don’t have enough iron in your system, you will be facing some economic challenges as iron allows for optimal plant development. As always, we are looking for ways to optimize our system. So, an iron deficiency will hurt our wallets and overall timeframe from a business point of view.

Why do we need to supplement iron?

Once again, it’s all about finding that nutrient balance in aquaponics as it is a closed, circulated system. So, if you think about it, it comes down to the fish feed. Commercial fish feed simply does not contain enough iron to satisfy the requirements of all living components in an aquaponics system. This is because even though the feed might have enough iron to satisfy the needs of our fish, there is not enough iron in the fish waste to satisfy our plants and their iron requirements. Therefore, we require iron supplementation if we’re looking to optimize our aquaponic farming system and avoid iron deficiencies. However, this process of supplementation requires close management to maintain the balance between the fish, plants and microbes in the system.

Aquaponic Iron Supplements

Iron bioavailability in aquaponics.

Unfortunately, it’s not as simple as throwing any form of iron into your system. This is due to the bioavailability of iron in different pH levels and aerated environments. Managing your iron can become tricky in an aquaponics system as iron takes on different chemical forms (ionic states) in the presence of oxygen. Iron is an element that is likely to react with other elements. Therefore, in an aquaponics system, you are likely to find iron in two states: the ferric state and the ferrous state.

Why is this a problem?

When iron is in the ferric state it is more oxidized and we face the problem of bioavailability. In other words, it is insoluble and the plants cannot absorb iron when it is in the ferric state. The ferric state is most commonly found in areas of high pH. However, the ferrous form of iron is soluble, found in areas of low pH. Plants will happily absorb iron in this form to be utilized for optimal growth. The problem arises when we consider the fact that an aquaponics system is a well-aerated system and we are constantly talking about the importance of monitoring your dissolved oxygen levels. Therefore, in the aerated areas of your system, which is usually near the roots of your plants, we face the issue of iron reacting with the excess oxygen and becoming the insoluble, ferric form of iron.

So how do I supplement iron into my aquaponics system?

We like to make use of a process called iron-fixation or chelation. Chelation is the process where insoluble ferric iron is bound to an organic molecule, making it soluble for plants. Our golden rule is to supplement our systems with chelated iron to ensure that the insolubility problem is avoided while still allowing our plants to get what they need.

There are two methods of supplementing your system, prevention or reaction. If you see that your plants are going a bit yellow between the veins on the leaves of young growth, you could be dealing with an iron deficiency. However, you can also use a preventative measure of supplementation and supplement in about 2 mg/L every 3 weeks according to Dr Rakocy at the University of the Virgin Islands. You can add your iron by dosing in your dosing bucket.

It all about the balancing act that we are constantly playing as an aquaponics farmer. So, make sure to give us a call or book a consultation if you are still unsure about how to walk the tightrope of iron in aquaponics. Additionally, you can find all your iron supplementation products at our store. Feel free to take a look!

Happy cycling!