Flourish Iron

Many in stock

Plant Supplement


**Valid on standard U.S. shipping to U.S. delivery addresses in the 50 continental states only. Not valid for international delivery address or U.S. territories addresses. Additional charges apply for rush shipping.

Shipping Rates and Delivery Times:

  • All free shipping options ship in 3-7 business days regardless of selected shipping option. (ex. Standard Shipping, Flat Rate Shipping, 2 Day Shipping)
  • Shipping options provided reflect other.
  • For expedited shipping, please Contact Us.
$ 10.99 USD
$ 10.99 USD

Iron is immobile in plants. This means that plants cannot divert iron from older leaves to new ones. Therefore, deficiency symptoms appear first on new or young leaves. Because plants use iron to produce chlorophyll, a lack of iron results in chlorosis, or yellowing, of the younger leaves. Stems may also appear short and slender. If the deficiency is severe and prolonged, each new leaf emerges lighter in color than the preceding leaf.

When choosing an iron supplement, it is important to know the distinction between the two forms of iron. The iron will be in one of two oxidation states: ferrous having a +2 charge, or ferric having a +3 charge. Ferrous iron, the preferred iron form and is soluble in water at any pH. Ferric iron, however, is only soluble below a pH of around 5.5; but if the pH is higher than 5.5, which more than likely it will be in a planted aquarium, the ferric iron will become insoluble and precipitate, settling in the root zone. Once this occurs, foliar absorbtion becomes impossible.

To overcome this precipitation, competing products employ a chelate of ferric iron: iron-EDTA. While this does keep it soluble, it has a couple of drawbacks with respect to foliar uptake of iron. (1) Iron-EDTA bonding is very strong, thus very little of the iron will be available to the plants over a given time frame and (2) Physiological energy must be expended by the plant in order to extract the ferric iron from EDTA-iron and then convert (reduce) it to the ferrous form. Our approach is different in that we use a complex (not chelate) of ferrous iron in Flourish Iron™.

Flourish Iron™ is a highly concentrated (10,000 mg/L) ferrous iron gluconate supplement. Plants are able to much more easily derive a benefit from Flourish Iron™ because ferrous iron gluconate is already in the ferrous form so they do not expend energy reducing it. Despite what other manufacturers may intimate, gluconate is not harmful to plants or fish. In fact, ferrous gluconate is better suited to foliar feeding than is iron-EDTA owing to the relatively weaker iron-gluconate bonding vs. iron-EDTA bonding. In addition, ferrous gluconate has the added bonus of being a source of carbon.


Use 1 capful (5 mL) for each 200 L (50 US gallons) or as required to maintain about 0.10 mg/L iron. For smaller doses please note that each cap thread is about 1 mL. Use a test kit to monitor iron concentrations. Due to rapid utilization, test within 30 minutes. Use as needed to combat signs of iron deficiency (usually seen in new growth) which include: chlorosis (yellowing) of tissue between veins and short and slender stems.


Amount per 1g

Iron (Fe) 1%

Derived from: Ferrous Gluconate


Refunds on live fish will be accepted up until 72 hours BEFORE the fish is scheduled to be shipped. No refunds will be issued on fish within 72 hours of the scheduled shipping time. Unopened dry goods will be accepted for a full refund within 7 days of receiving. Return shipping is buyer responsibility.


I guarantee my fish will arrive alive. *you must be available to receive the package the day of delivery.”

If a fish expires in transit, I will replace the fish, however, you will be responsible for the shipping costs. The replacement fish must be of equal or lesser value than the initial purchase.

However, we are not responsible for the mishandling of your package during transport. Once the package is in transport, we will not be held liable for any damages to the package. We most certainly may help redirect you to the carrier responsible.


Please take a picture for us showing the loss- it can just be a picture taken with your smart phone and email to DOA@kingkoigoldfish.com. If approved, we will coordinate with you to replace the fish with a fish of similar color and size, AT OUR DISCRETION. You will still be responsible for any shipping costs associated with the replacement. We work very hard to make sure that you receive your fish alive.


We can ship to virtually any address in the United States (Including Hawaii and Puerto Rico).

When you place an order, predetermined shipping options have been set to reduce shipping costs. Such options will be given to you during checkout. If you have any questions or concerns regarding shipping costs, please don’t hesitate to reach us at sales@kingkoigoldfish.com.

Please also note that the shipping rates for many items we sell are weight-based. The weight of any such item can vary based on quantity so they have been automated using our proprietary algorithm. To reflect the policies of the shipping companies we use, all weights will be rounded up to the next full pound.

For more information, please visit our Shipping Information Page or our Return & Refund Policy page

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