The Planted Tank Forum - View Single Post - Not seeing value in "megadosing" nutrients
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post #17 of (permalink) Old 10-16-2020, 08:45 PM
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I dose .1ppm iron daily (.7ppm weekly), but that is all gluconated (Seachem Iron). Because of my level one UVS, I cannot use chelated iron, such as EDTA or DTPA. Generally, you need to dose more gluconated iron that EDTA or DTPA forms because it is consumed by plants so rapidly. After going back and forth with Seachem on how to determine how much to dose (their directions are a little misleading), they advised to dose enough so that ferrous iron tests show zero iron after 20-30 minutes. During that time, the plants will uptake virtually all of it. In my case I could actually dose higher than I do and remain within these test parameters. This is because it is in the ferrous form and not the ferric form found in chelated versions, which are designed to last much longer in the water column (up to several days). Additionally, the gluc iron is not dependent upon pH levels.

As far as test kits for iron are concerned, after trying a few different kits, I found that the Nutrafin kit (may be labeled under the Fluval name) is good at detecting both types of iron. I donít have the Hanna version because I donít think it is important to test for iron at that price since iron testing is so questionable in both results and value, as @Edward pointed out. However, I do use Hanna for other types of tests and would expect their iron test to be good, as well. I found Seachemís test to be good with ferrous iron (which is their product), but not very good for ferric iron. As I understand it, the chelated bond has to be broken down by these types of reagents before actually being able to measure the ferric iron (this is the reason for the lengthy time to measure EDTA and DTPA iron) and many test kits arenít good at doing that. Conversely, some were not good at measuring ferrous iron.
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