Review: Abdel Rahman El Gamal (Founder of the website)
Iron deficiency is common in aquaponic system and may lead to several adverse effects on the plants which turn pale and yellow as the iron deficiency compromises the plants ability to make chlorophyll. Iron deficiency could be detected through visual inspection. In new plant growth, the iron deficiency becomes evident when the entire leaf shows a yellowing or Chlorosis, however in mature leaves, there is a very noticeable and characteristic when the leaves of most plants start to yellow, while the veins in those leaves remain green.
In order the address iron deficiency problems, adding iron is a typical practice in aquaponics system. Chelated iron is the form used in aquaponics system whereas chelated iron compounds are available in different commercial products such as Fe-EDTA, Fe-DTPA, and Fe-EDDHA. The effectiveness of different forms of chelated iron is influenced –to a large extent- by water pH. In aquaponics as the pH may go to 8 and above, the Fe-EDDHA has been found effective at a wide range of pH making it the most usable form of chelated iron in aquaponics even though the product is expensive and it turns the water color into red. However, there may be different opinions in regard to the iron forms used in the system based on field experiences, availability of the product along with the cost. Also, the pH of water may favor one compound over others.
Added iron would depend on several factors, including the amount of iron already present in the water whether within the system or the water source as well the uptake of iron by the plants. Also, it is important to note that the water volume in the system includes fish tank, water in the sump and water in the grow beds. A standard dosing of 2 mg of pure iron/liter of water every 3 weeks is the industry standard. The actual quantity of the chelated iron compound added would be based on the percentage of iron in a given compound.
While iron deficiency has its negative effects, the oversaturating of iron in aquaponics poses negative effects as the over-dosing of iron can impede the plants ability to take up nutrients and absorb sugars and may eventually leads to death.
In order to maintain the proper all-time iron concentration in aquaponics and not waiting for the deficiency signs to appear and in the same time avoiding the iron overdosing, test kit for iron could be used. In general, iron level should not be allowed to reach as low as 1.5 mg/l.