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Flourish Iron - Maintain .1 ppm ...or not?

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  • Flourish Iron - Maintain .1 ppm ...or not?

    Your directions suggest that Flourish Iron should be dosed to maintain .1 ppm. Of course, this may mean that a very heavy dose, far above .1 ppm, would be required, the amount depending upon how long the .1 ppm is to be maintained between dosing. I am concerned about the potential for iron toxicity in following this logic.

    You also suggest testing within 30 minutes because of rapid utilization. This seems to imply that you expect that there should be no readable ferrous iron remaining after 30 minutes.

    So, the question is: which is it? Do you recommend maintaining .1 ppm 24/7 or do you want to see all of the iron gone in no more than 30 minutes after dosing?

  • #2
    Hello Deanna,

    Thank you for your messages. When providing dosing instructions, we strive to both provide the end user with useful aquarium maintenance information as well as specific information as to how the dosing of our products may differ from more conventional fish keeping wisdom. With regards to iron dosing, conventional wisdom is that the iron concentration should be maintained at approximately 0.05 - 0.1 mg/L for optimal iron utilization. However, it is also true that our product is utilized so rapidly that this concentration will not be sustainable long-term in the aquarium without significant overdoses, which we do not recommend.
    So to answer your question, if you are using Flourish Iron, you do not need to shoot for testable iron levels 100% of the time - a good dose every day or every other day will suit the iron needs of the plants because of rapid utilization. For this reason Flourish Iron should be measured within 30 minutes of dosing to ensure that the concentration you measure is consistent with the amount you dosed.

    Flourish Iron is a ferrous form of iron. It can be taken in by leaves, stems and roots and is the most accessible form for plants. Because it is a ferrous gluconate iron, it provides iron in the proper form for plants so that they will not have to expend energy to break down the iron. In addition the gluconate provides a source of energy for the plants. We have chosen this form as it is the most preferred form for plants and provides ease of dosing since the plants will in essence take it in easily like a sponge. Plants are able to much more easily derive a benefit from Flourish Iron™ than from EDTA-iron sources because all EDTA iron is in the ferric (Fe+3) state. Since plants require iron in the ferrous (Fe+2) state, additional physiological energy must be expended in order to extract the ferric iron from EDTA-iron and then convert it to the ferrous form.

    Therefore, our solution is that we provide the more conventional dosing recommendation, which provides your plants with the amount of iron needed daily, while noting that Flourish Iron will be utilized rapidly. Long-lasting iron readings in the water mean that the form of iron that is present in the water is difficult for plants to use.

    Hope this clarifies and let me know if you have any other questions!

    TechSupport SM


    • #3
      Thank you.

      Yes, I understand what the gluconate form does and it’s benefits …and I like it for that reason. I’m just a little confused about the conflicting statements made on Seachem’s website regarding maintaining .1 ppm indefinitely but to expect it to disappear after a half-hour, as many people are.

      However, I think you just provided a much clearer path. You seem to be saying that it is not realistic to maintain a .1 ppm level in a planted tank having good growth rates. You are saying that - this is the operable part - maintaining a .1 ppm level for a half-hour is a good target. Is this correct?


      • #4
        Yes that is correct!

        You are very welcome! I am glad that clarified things for you, and hopefully for others! :)


        • #5
          I will lead with my direct question and follow it with the explanation of why am I asking?
          The question is, "At what concentration will inhabitants begin to experience iron toxicity?"

          I noticed symptoms of iron deficiency in my plant inhabitants about 10-12 months ago so I chose this product to supplement. Initially I dosed sporadically when I saw one plant or another starting to really dwindle. I have since decided to regulate a dosing regiment. I had the same initial reaction to the dosing instructions as the OP. The responses from support were helpful to understand that this target concentration is not to be maintained, rather "conventional wisdom" suggests 0.1mg/L of Fe2+ is to be the MAXIMUM target concentration BEFORE uptake by the plant inhabitants. Okay, this makes sense.

          My persisting confusion is w.r.t. the instruction "Use 1 capful (5mL) for each 200L (50 gallons) OR [conventional wisdom]".

          If I follow this dosing of 5mL/200L the resultant concentration in my 60gal tank would be 0.25mg/L. If I simply drop the 5mL into the tank it would be a similar situation at 0.219mg/L... So basically two and a half times the concentration deemed "safe" by "conventional wisdom". This is concerning to me; Please help.
          Last edited by DerWolfmann; 12-05-2019, 16:34.


          • #6
            Thanks for the post, DerWolfmann!

            We recommend maintaining an Fe level of about 0.10 mg/L. Iron is utilized quickly in an aquarium, so you will want to initially exceed 0.10 mg/L in order to prevent iron levels from falling below that level. To accommodate for its quick utilization, the standard dose of Flourish Iron will raise iron by 0.25 mg/L, but will not remain there for very long as it gets depleted quickly. The plants will only utilize what they need and the rest will either get oxidized or precipitated. According to our dose calculator, if you are starting with zero iron and are wanting to get to 0.1mg/L exactly, you would only need to add 2.4 mL or half a cap, however, because of what we have discussed above, it will be gone almost immediately and you will not be able to maintain the 0.1mg/L in the water column. Like we mentioned in the above post, Flourish Iron provides the iron in the preferred bioavailable state, so if you are dosing it regularly, we can assure you that the plants are getting the proper amounts of iron that they need. That is not to say that if you have a ton of iron loving plants in your system, you may require more Flourish Iron than recommended.

            As for toxicity, from what I can find it only is the ferric form of iron that can become toxic to aquatic inhabitants and Flourish Iron is in the Ferrous form, therefore, is not toxic.

            Here are a couple of articles if you're interested:

            Iron is a common pollutant in waters near coal and hard rock mine disturbances. The current 1000 µg/L total recoverable chronic criterion for iron (Fe) for protection of aquatic life in the United States was developed using very limited ...

            I hope this helps! Let us know if you have further questions!