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PMDD Iron Levels
Kelly wrote: "Ok, so now I have a bottle of my very own PMDD and I have
the Sears-Conlin paper about dosing. But there's something on which I'm
not quite clear. If your Fe levels are below .1 ppm (or is it 1 pmm, I
forget), how can you "ramp" that up without causing major disturbances?
Right now I'm dosing according to Sears-Conlin, and adding a couple of
extra drops til I get the recommended amount."
It's 0.1 ppm iron. The hardest lesson I learned about using PMDD was
NOT to ramp up to 0.1 ppm. There has been quite a bit of talk on the
APD about iron levels in the standard PMDD mix. Iron is not one of the
nutrients we can vary since it comes as a fixed component (7% I think)
of the micronutrient mix. Some of us think the iron levels might be a
bit high. At least in my case (using soft Hetch Hetchy water here in
San Francisco) I had continual algae problems (thread and brush) if I
maintained 0.1 ppm iron levels.
Another problem is that the iron test kits don't seem to be very
accurate and may or may not measure chelated iron very well. I can tell
you that my Hach and LaMotte iron test kits (I used to be into this iron
stuff! :-)) never quite match when reading the same sample. Others have
reported that the cheaper kits seem to report 0.1 ppm or nothing-so
folks might think they have a certain amount of iron when in fact some
of the kits may be reading iron more like a switch: either you have some
or you don't.
If memory serves (and it may not) a few months ago Paul Sears mentioned
the idea of just keeping iron levels at measurable levels rather than
0.1 ppm. If you have some iron in the water column which your test kit
can pull out and read, that's enough; in fact, it's plenty. And some
folks, Diana Walstead comes to mind in particular, believe they control
algae by carefully limiting iron levels in the water column.
Finally, it's my guess that you're asking for (algae) trouble if you
"ramp up" your PMDD in a tank without CO2 supplementation and good
lighting (I don't remember if you mentioned your lighting). I would
just dabble in a few drops per day and watch your plants and see how
they respond. If your plants are chlorotic, they should perk up nicely
in a week or two. If they're getting enough iron, adding more isn't
going to help.
Good luck and let us know how it goes, Steve Dixon