re: PMDD Tropica Mastergrow

---------- Forwarded message ----------
From: psears at emr1_NRCan.gc.ca (Paul Sears)
Message-Id: <9701291344.AA19389@emr1.emr.ca>
Subject: Re: PMDD Tropica Mastergrow
To: Aquatic-Plants at ActWin_com
Date: Wed, 29 Jan 1997 08:44:42 -0500 (EST)

> From: Kevin Conlin <kcconlin at cae_ca>
> I must confess that when I developed the original recipe I based
> the %Mg and K on the Tropica formula.  Since then I've reduced
> the Mg to 40% of the original value and cranked the K way way up.
	From Karen Randall
> Sorry, Paul, when the term "PMDD's" was first being thrown around, I
> thought I remembered that someone was using the percentages in Mastergrow
> as the model for PMDD.  I know that your addition of N was an added step to
> reduce P in nitrogen limited tanks.  Sorry if I mislead people.

	I suppose I should have said "I", not "we" in my previous posting. :)

	I have always added the various components on a daily basis, rather
than use a mixed stock solution.  I vary the amounts of each according to
what is going on in the tank, both observation of plants and algae and
NO3- and Fe readings.  Kevin uses the "PMDD" approach, and has changed the
recipe more than once, again according to (rather longer term) observation.

	I am now of the opinion that if there is little nitrate in the 
water supply and no major source of potassium in the substrate, most tanks are
short of potassium.  This then means that the plants cannot use the 
nitrogen, and nitrate builds up.  I think that a lot more tanks would be
"nitrogen limited" if potassium were supplied adequately.

Paul Sears        Ottawa, Canada

Finger ap626 at freenet_carleton.ca for PGP public key.