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Re: Diagnosis Request

On Fri, 5 May 2000, Birdy wrote:

> I am trying to deturmine what nutrients may be missing from my tank.  I have
> lots of new growth on my Amazon sword plants, but the leaves are lighter
> green, and are all leaf, no stem.

If this plant was recently purchased and the lighter new leaves are the
first leaves that have grown in you tank then you may just be seeing the
difference between emersed growth (usually dark green with petioles as
long or longer than the leaf blade and leaf blade generally oval or
vaguely heart-shaped) and submersed growth (often lighter colored, with
brownish veins, petioles shorter than the leaf blade and leafe blad
lanceolate).  That wouldn't be a nutrient problem.

> Other plants have large growth of leaves, that are either lighter green, or
> in one case, very yellow.

Several nutrient shortages can cause leaves to yellow.  Among the
shortages we usually see, low iron will cause yellowing in new growth.
Low nitrogen will show yellowing in older leaves that were initially
green.  If you weren't already using an iron supplement then an iron
shortage seems fairly likely.

> I have a green water algae probem which I am trying to solve by the "Get the
> plants to out-compete the algea" method.  So I am trying to add plant
> nutrients one at a time, avoiding any phosphates.

I recently read an article by Ole Petersen where he says that
phytoplankton are so effective at using dissolved nutrients that they can
essentially prevent plants from getting anything added to the water.  As a
result you may not be able to use additions of dissolved nutrients to
encourage your plants to out-compete the phytoplankton.  I usually filter
the green water to get rid of the phytoplankton and count on competition
from healthy plants to keep it from recurring.

> Yesterday I began adding a iron supplement, so it's too early to tell what
> the effect of that is.  What would you try next?

Give the iron supplement a little while to work.  If it you had an
iron shortage then you should see improvements on the first new
leaves developed after you add it, but it may not be immediately
obvious, especially if growth is slowed by the green water.

Roger Miller