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Re: Help with PMDD

> I'm going to try making PMDD for the first time and need some advice
I switched to PMDD about 2 months ago on my 20Gal tanks and the results were
very good. I used the same formula that you just described but cut the
quantities down (500 or 300ml of PMDD is way too much). Here it is:

#1 (in 160ml water):
1 tsp Chelated trace mix (7% Fe, 1.3% B, 2% Mn, 0.06% Mo, 0.4% Zn, 0.1% Cu,
1 tsp MgSO4.7H2O
3 tsp K2SO4
- dosed daily at 0.43ml or 8 drops

#2 (in 160ml water):
2 tsp KNO3
- dosed daily at 1.5ml while nitrates are low

I actually made two solutions, both in 160ml of water. Having KNO3 separate
comes in really handy when you need to control the nitrate levels in your
tank. I have also decreased the MgSO4 concentration since I have roughly
75ppm Mg from the tap (yours might be different). I have also increased the
K2SO4 amount since according to my calculations 2 tsp would not have brought
the potassium levels high enough. With the above formula the ratios of the
different elements vs Fe are (keep in mind that I used a different trace mix
from yours from http://www.hydroponics.com/info/index.html, see above

Element, G/ltr--Ratio to Fe (for #1)

N, 0--0.00
K, 19.35--14.77
S, 11.39--8.69
Mg, 2.71--2.07
Fe, 1.31--1.00
Mn, 0.37--0.28
Zn, 0.075--0.06
Cu, 0.02--0.02
Mo, 0.01--0.01
B, 0.24--0.18
Co, 0--0.00
NO3, 0--0.00
SO4, 34.21--26.11

Dosing #1 as above (8 drops/day or 0.43ml/day, not all drops are equal) it
took 2 weeks to initially get to the 0.1ppm target for Fe but it took
another month before the level was actually stable (meaning it went back
down after the first two weeks). I have since dropped the dose to 6
For #2 I was dosing at the 1.5ml/day and didn't get any nitrate readings for
a whole month. I doubled it to 3ml/day until it brought nitrates to about
10ppm and then dropped it back to 2ml/day.
I should point out that I have a light fish load of about 0.75cm/Liter.
Without adding the KNO3 the plants used to exhibit nitrate deficiency and
growth was quite poor. You can also probably notice that I used roughly 5
times the amount of #2 solution as compared to #1. Keeping KNO3 in #1 would
make that difficult.

I hope this helps.

Adrian Banica
Edmonton, Alberta