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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 
     year now.
     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.