Randy Holmes-Farley
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My Tank Thread
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I doubt it, unless you are intentionally dosing unusually large amounts of iron. I do not think this is the cause of low phosphate.So that is why my phosphates are dropping, Ever since I started dosing iron. Now I have to dose phosphate so it does not drop to zero. Phosphate levels have been 0.12-0.06 for several years, now drops to 23, 17, now 13.
Let's look...
A typical dose of iron (my dose; see below) is, say, 2 ug/L. How much phosphate could that remove even if it ALL became ferric phosphate?
FePO4 is about 1/3 iron and 2/3 phosphate by weight.
So 2 ug/L of iron might combine with 4 ug/L of phosphate, or 0.004 ppm.
Typical foods daily add 0.02 to 0.3 ppm per day:
Aquarium Chemistry: Phosphate And Math: Yes You Need To Understand Both
Foods are by far the most important source of phosphate in most aquariums. In considering whether sources of phosphate other than foods are important, one must carefully look to the actual amounts involved to determine whether other sources are even worth trying to minimize.
reefs.com
Thus, if you dose iron at my done once a week, you are only possibly precipitating 0.004 ppm out of a weekly food addition of 0.14 to 2.1 ppm of phosphate, or only 0.2% to 3% of the total phosphate.
This is from my Triton testing article:
Iron (Fe). The natural iron level varies a lot with depth, but surface seawater may have only 0.006 µg/L. The Triton LOD = 0.3 µg/L. I dose iron, and when I dose it I boost iron to roughly 1-2 µg/L, which would be detectable. This sample was taken more than a week after the last iron dosing, and none was detected as it gets depleted in the meanwhile. I’ve not yet seen a Triton test result for a real aquarium sample that had detectable iron, but that doesn’t mean these tanks are necessarily deficient. Iron is also a case where the form is critical, and ICP cannot distinguish form. Binding to organic matter, for example, can alter the bioavailability of iron.