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> On Tue, 2 Feb 1999, Grover wrote:
> In addition recent posts have been pointing out that the test
> > kits used are not measuring chelated iron. The forms of iron
> > registering on the tests are not the ones being used by plants.
I don't think that it is essential that we know the exact amount of each
form of iron in the water. That would be nice, but if my test kit measures
0.1 ppm iron and that grows plants for me, then I'm happy. Probably only
Paul Sears and/or Kevin Conlin knows how that number was arrived at. (what
test kit was used to determine 0.1 ppm) Are different brand test kits
measuring different things? I don't know.
I do know that when my LaMotte test kit measures 0.1 ppm, I am close to
growing thread algae. For me, 0.05 ppm works well. I don't care what I'm
measuring if I know that beyond 0.1 ppm on _my test kit_ leads to algae.
> If you have rising nitrates, then PMDD probably isn't the indicated
I don't think that I totally agree with this statement. It is possible that
potassium, magnesium or some other element may be in short supply thus
keeping the plants from utilizing the available nitrates. Perhaps the tap
water is high in nitrates or the fish load is high. The real beauty of PMDD
is that it can be custom tailored to your needs. The trick is to figure out
what it is you need.
> PMDD is formulated for the case where nitrogen is limiting
> (absent in the water and in the substrate) and the water contains
> phosphorus levels.
I believe that PMDD is formulated to eliminate _all nutrient deficiencies_
> In your case with rising nitrate levels it appears
> that something other than nitrogen is limiting. That could be the light.
> It might be something else.
This, I agree with. Either your test kit is bad, or your problem is not
Nitrogen related. Like I said, the trick is to figure out what it is.