Seachem Flourish Iron

Iron is immobile in plants. This prevents plants from transferring iron from older leaves to new ones. Therefore, deficiency symptoms first appear on new or young leaves. Since plants use iron to produce chlorophyll, iron deficiency results in chlorosis, or yellowing, of the younger leaves. The stems may also appear short and thin. If the deficiency is severe and long-lasting, each new leaf will appear lighter in color than the previous leaf.

When choosing an iron supplement, it is important to know the difference between the two forms of iron. The iron will be in one of two oxidation states: iron with a charge of +2 or iron with a charge of +3. Ferrous iron, the preferred form of iron, is soluble in water at any pH. However, ferrous iron is only soluble below a pH of about 5.5; however, if the pH is higher than 5.5, which is most likely to be the case in a planted aquarium, the iron will become insoluble and precipitate out and settle in the root zone. When this occurs, foliar absorption becomes impossible.

To overcome this precipitation, competing products use a chelate of ferric iron: ferric EDTA. While this keeps it soluble, it has a couple of disadvantages with respect to foliar iron uptake. (1) The iron-EDTA bond is very strong, so very little of the iron will be available to the plants in any given time frame, and (2) Physiological energy must be expended by the plant to extract the ferrous iron from the EDTA iron and then convert (reduce) it to the ferrous form. Our approach is different in that we use a complex (not a chelate) of ferrous iron in Flourish Iron™. Flourish Iron™ is a highly concentrated (10,000 mg/L) ferrous gluconate iron supplement. Plants can benefit much more easily from Flourish Iron™ because ferrous gluconate is already in the iron form so they do not expend energy reducing it. Despite what other manufacturers may suggest, gluconate is not harmful to plants or fish. In fact, ferrous gluconate is better suited for foliar feeding than ferrous EDTA due to the relatively weaker ferrous-gluconate bond compared to the ferrous-EDTA bond. In addition, ferrous gluconate has the added bonus of being a source of carbon.