Seachem Flourish Iron is highly concentrated (10,000 mg/L) source of ferrous iron gluconate supplement designed for use in delicate planted aquariums. Plants use iron as a way to produce essential chlorophyll, but a lack of iron will result in chlorosis, or the yellowing of the younger leaves with short and slender stems. If the deficiency maintains severity and duration, each new leaf that emerges will be lighter in color than the preceding leaf. Plants are able to better utilize this formula due to the fact that ferrous iron gluconate is already in the ferrous form so plants do not expend additional energy trying to reduce it. Ferric iron is only soluble below a pH around 5.5, but this will be significantly higher in planted aquariums, rendering this type of iron useless. The ferrous iron found in Seachem Flourish Iron is the preferred iron form as it is an excellent source of carbon and is soluble in water of any pH level, making it more versatile and functional for a variety of different water parameters for planted aquariums. Additionally, the ferrous gluconate found in this formula is better suited to foliar feeding than iron-EDTA, allowing your plants to grow and develop at a quicker rate.