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RE: Flourish Iron, Correct dosage & procedure

Every so often a posting comes along with a somewhat critical undertone.
Unless the questions within the posting are worded in such a way that it
is easy to understand what the poster wants to learn, it is quite
difficult to respond to that posting. If there is a slight sarcastic
undertone or something which can disturb a few senstive people, its
likely to attract one or two somewhat cynical responses. Don't be
surprised when it happens to you if you have a habit of making off-hand
even mildly critical remarks.

Oh well.

From the beginning, the APD has been a rather polite forum compared to
the newsgroups. That's not to say we haven't had a few colorful
discussions now and then.   :%>   Many of the regular posters have been
here for a long time and we know one another quite well. For the most
part, the folks are pretty tolerant of newbie questions.

There is one important difference between this mailing list and the
newsgroup. Anyone can post to a newsgroup but here if someone becomes an
annoyance, BEWARE lest the wrath of the ListMom fall upon thee! I
anticipate that the last posting by Mr Hudspeth is going to attract a
lot of "off-topic" responses.

Oh well. 

I have a feeling the ListMom will call for a quick end to the thread

OB aquatic plants content:

It is extremely difficult to predict the amount of Fe that a planted
aquarium is going to consume. That's one reason why the PMDD regime
suggests that you monitor Fe levels with a reliable test kit and adjust
the dosage to maintain 0.1 ppm Fe. Once you find the appropriate dosage,
you don't need to continue monitoring (maybe spot checking) because you
should have found a reasonable dosage that is neither so high that it
might encourage the growth of algae nor so low that the plants don't
maintain the desired growth rates to keep ahead of algae.

You don't HAVE to use a test kit to arrive at that dosage; you can do it
by looking at the plants but I don't know how I could explain to someone
exactly HOW to find the sweet spot. Here's one way to make an educated
starting guess.

Calculate the dosage so that you could achieve say 0.2 ppm of Fe in the
replacement water which you are going to change each week. In this way,
even if your plants use zero Fe and it never breaks down, you cannot
exceed 0.2 ppm final concentration in the aquarium after many many water
changes. In turn the lower limit if you were replacing 25% of the water
at each water change, if all Fe were consumed at the end of each week,
would be a final concentration of 0.05ppm. This should be quite
adequate. Instead of adding the dose all at once, divide it by 7 and add
it daily. You could probably dose at the rate of 0.01 ppm each day even
with less frequent water exchanges. Any of you PMDD users estimate what
your daily consumption rate is in ppm?

Now I have a question, let's assume that the rate of decay of chelated
Fe in solution is constant (in proportion to the concentration). Can
anybody estimate the half-life of Fe-EDTA or Fe-DPTA at 78F? Are we
talking a week or a few days? I suppose it really depends too much upon
the bacterial population in the water and so maybe there is no
meaningful answer to this. Can anyone provide any experimental data as
to whether the aquatic plants or the bacteria in the aquarium are the
primary consumers of chelated Fe in solution?

Steve Pushak                              Vancouver, BC, CANADA 

Visit "Steve's Aquatic Page"      http://home.infinet.net/teban/
 for LOTS of pics, tips and links for aquatic gardening!!!