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Re: PMDD confusion
I want to applaud Tim for his detailed postings on PMDD. He has
obviously spend a lot of thought and time on this subject. Thanks!
>Oh, as I've pointed out,your level of Fe dosing does seem high. Where
>have your actual Fe readings come in?
(Tim calculated an Fe conc. of 0.64 mg/l, based on my dosage).
I do not measure my Fe, for two reasons:
1) I doubt I can accurately measure iron in my aquarium, given all
the problems others have reported with various Fe test kits. I feel
the error associated with the kits is too great to allow accurate (+/-
0.1 ppm Fe) dosing of PMDD. I just use the recommended dosage, and
hope for the best.
2) My plants do not display any symptoms of too little/too much Fe
(i.e., I get rapid growth, no chlorosis, and no hair algae). So, I
always thought I had the proper dosage. I've used this amount for a
However, unlike Paul I have never used a UV sterilizer on my tank, so
now I am concerned I have been overdosing with Fe. I haven't
experienced any problems, though.
I do measure my NO3 (Seachem low range nitrate, with foil-packed
reagents dated to ensure freshness), and I am confident with the
results. You calculated my nitrates to be 9 mg/l, assuming no uptake
by plants. I measure 3 ppm, which implies my plants are using about
0.6 g of NO3 per week (based on 1.5 g of KNO3 added/week with a 10%
water change). Of course, this assumes no measurement error, no
contribution by my fish, and no de-nitrification in my substrate (BAD
assumptions!). I have a heavily planted tank with a soil substrate,
CO2, and good growth. If I knew % nitrogen by plant weight, I could
get some rough estimates of plant growth.
Mark in soggy Austin, waiting for the approaching hailstorm.