Iron is one of the plant nutrients that must be supplemented in almost all aquaponics system. In the aquaponic solution, iron is commonly available in one of two forms- reduced, soluble ferrous iron (2+), and insoluble oxidized ferric iron (3+). Ferrous iron is available to plants (soluble). Ferric iron is not (insoluble). This is important to understand, because ferric iron is the more oxidized form, whereas ferrous iron is not. In short, as soon as ferrous iron becomes soluble in aerobic environments of aquaponics it is often oxidized, becoming ferric iron or reacts with other compounds to become biologically unavailable (especially at high pH values when different hydroxides are formed). Now, this relationship between oxygen and iron isn't a full time thing. In reality iron is flitting between ferrous and ferric states, but the dominant state in high pH and oxidized environments is ferric- and this means that your plants cannot take it up. Chelation is accomplished by special organic molecules called chelating agents. These are organic molecules that are specially designed to capture, or "dissolve" metals, of which iron is one. In the plant world, chelatins are produced by the plant roots and leaked into the soil capture and deliver insoluble iron ions. The most common forms of chelated iron are: EDTA Fe: This is a slightly toxic form that aquaponic practitioners should not use. This type of chelated iron is commonly used as an herbicide to kill broadleaf weeds. It should not be used just because of its toxicity, but also because it typically only effectively chelates iron up to the pH range of 6.3 or 6.4. Above this range, it is not a stable chelate. So, using EDTA Fe in your consistently pH 7.0 system represents a significant amount of money wasted in comparison to other forms of chelated iron. For this reason, it is recommend that AP practitioners do not use EDTA Fe. DTPA Fe: This is what it is recommend for most systems at pH values between 6 and 7.5. WHICH IS WHAT IS AVAILABLE HERE at Aquaponics Growing Supplies! EDDHA Fe: This is what it is recommend for systems which have pH values up to 9.0 (let’s hope your pH never gets that high!), and the best all-around form of iron chelate, especially for starting systems. Effective at a broad pH range, EDDHA Fe maintains iron solubility in almost all of the water conditions encountered by startup aquaponic systems. HOWEVER, IT DOES TURN YOUR SYSTEM WATER RED! Therefore, you are advised to first setup and cycle your system to ensure nitrification process is developed and rest assure your system PH will continue to lower as a result of nitrification and you can start using DTPA Fe once it hits PH 7.5 and below. Instruction of use is provided in the packaging. Please visit our Shopee store for more products and enjoy savings on shipping fee when you purchase our other products.