jgreene wrote in message . ..
I have been dosing my plants with pmdd for less than a month and
noticed a strange thing: no matter how much I dosed, I could never
detect any iron. I always figured it was because my iron tester
(seachem) is VERY difficult to read at low levels (.1ppm). So
yesterday I did a test, I put 1 drop of pmdd into the cuvette used to
test iron and filled it up with blank water and tried to detect iron.
There was none detected. I then put in a small amount of the solid
trace element mix and dissolved that in the cuvette and still I
couldn't detect any iron. I got the materials to make the pmdd from
homegrown hydroponics. My guess is that the compound that they use to
chelate the trace elements binds stronger to the iron than the
material in the iron tester can bind to the iron. I was just
wondering if anyone else has experienced this problem, and how people
get around having such problems.

Jason Greene

Iron test kits are very poor at determining bio available Fe.
Even good ones.
PMDD was developed with the notion that excess iron causes algae. But
PO4 is the limiting nutrient also.

Only _one_ nutrient will be a limiting nutrient if one is present.
Not two.

So the advice based on that is not logical unless you plan on bouncing
between Fe and PO4 being your limiting nutrient.
But the notion of limiting a nutrient is flawed for winning the algae
battle.
Algae are quite able to live on far less than plants are.
Limiting nutrients hurts the plant's growth rates much more than it
does the algae.
PMDD was also designed using T-12 bulbs, low light tanks(and large
tanks) with lower CO2 than I would recommend even with low light.

If you have 2w/gal of Powercompacts etc, that's a fair amount more
light.

I add around 3x the recommened dosings of traces. Always have
Claus who just gave a talk at the AGA meeting suggested folks to do
what I have already been doing for many years back in 1998 when he
spoke at SF, CA if the tank is fully planted, with CO2 and good light
etc.

He's not a bad guy to trust He and I found it to be true completely
independantly .

Regards,
Tom Barr