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re: Problem growing Amazon swords (fwd)

---------- Forwarded message ----------
Date: Fri, 22 Nov 1996 12:10:36 -0600
To: Aquatic-Plants at actwin_com
From: steveb at bga_com (Steve Benz)
Subject: Problem growing Amazon Swords

>On to another problem.  In a different tank, I can not seem to get
>Amazon Swords to grow.  The leaves die back and are replaced by much
>smaller ones (E. bleheri, E. paniculatus).

This is exactly the pattern I used to see in my tank.  At first, I was
using Dupla drops&tabs.  A fellow Austinite (Mark Fisher) has a tank
where swords grow well - he uses PMDDs and has a soil substrate.  Since
I thought PMDD's were a knock-off of Dupla, I figured the trick was the
soil.  So I plucked out one of the swords and potted it up (with soil.)
Sure enough, within a week the sword came back and started growing.
6 weeks later, it was far bigger than the "control" plant.  I thought
I had an answer.  So I posted my results to this group.

That was a fatal mistake.  The sword immediately stopped growing?!
I suppose there was something in the soil that was missing in the
Dupla fertilizer, but after 6 weeks, it was depleted.

Several weeks later I borrowed 16oz of PMDD's from Mark.  For the first
few weeks of use, they had no effect whatever, then, just as the supply
ran out, visible (positive) effects were seen on both sword plants.
I mixed up my own batch and now all sword plants are growing fairly
well.

Since this wasn't a controlled experiment, I'm not comfortable saying
that PMDD's did the trick.  Also, I'm not comfortable with the fact
that I don't know why they did the trick - perhaps the tank was
limited by K, perhaps it was limited by Mg, and perhaps it was
limited by iron (PMDD's seem to supply more of all 3 than the
Dupla regimen.)

Given that other people can grow swords just fine with Dupla fertilizer,
I'm tempted to go with Mg as the source of the problem.  Austin water
is fairly hard (KH of 3-4, GH of ~11).  It may be that the ratio of
Mg ions (in particular) is low, and that this adversely impacts some
plants' ability to aquire it.

                                        - Steve
------
Steve Benz (steveb at tall-tree_com)   |   Tall Tree Software Co.
http://www.tall-tree.com            |   Ph/Fax: 512-453-4909