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Re: Rotalla wallichii Survey Participate!!!!

I have had similar experiences to those reported by Cavan with Rotala
wallichii, and I have a hypothesis that when it goes down hill, the problem
may be too many nutrients, rather than too few.  My hypothesis is that
wallichii is a high-light, low nutrient plant, and that some other members
of the genus, Rotala are, too, such as macandra and rotundifolia (=indica).
About a year ago, someone on this list reported a problem with indica that
he called, aptly, "little-leaf" condition.  The leaves get smaller and
smaller, until they were hardly visible.  Then the stem tip died.  It
looked like it might be calcium or boron deficiency, but it persisted when
those two nutrients were added.  I have seen the same thing in indica when
it was in a heavily fertilized tank.  When I moved it to a new tank, where
I had a good supply of calcium (from ground limestone), along with excess
potassium, magnesium, and sulfate, along with a good supply of
micronutrients, but very restricted in nitrogen and phosphorus, the plant
grew very well, with nice pink leaves.  I have been ignoring the tank for
many months, and the indica is still looking pretty good, whereas some
other species---Hemianthus umbrosum, Didiplis diandra, and Cardamine
lytra---have just about died out completely. I have some Bacopa monnieri in
there that is still alive, but has lost a lot of leaves.  The other plants
with the indica that have held their own in spite of the neglect (no CO2 or
nutrients for months---This is a tank without fish---) are Heteranthera
zosterifolia, and Cryptocoryne walkeri.

So, it looks like indica is a plant that can hold its own under crowded,
low nutrient conditions, as long as it gets light.  I don't know of any
scientific support for the notion that some species can be hurt by other
than very low concentrations of N and P, and that is why I don't feel
highly confident in the hypothesis. It goes against a large body of
literature in plant nutrition.   However, I would like to try to test this
hypothesis some more, if I have the time and some tank space. If it isn't
actually high N & P causing the damage, then it may by some kind of
associated conditions in a heavily fertilized tank.

Indica is a plant that is much less delicate than wallichii or macandra.
However, it seems to show similar symptoms.  When I have had macandra and
wallichii doing well, they were in a crowded tanks where I would see a
definite increase in growth in all plants if I add a small piece of dried
liver for fertilization.

 I have a small amount of wallichii, that has been existing as a floating
plant for about 8 months.  I have just planted it, and will watch it
carefully.  One interesting thing I saw with wallichii was that I once had
a very beautiful, healthy-looking stand of it that was overspreading my
tank and shading out other plants.  When I trimmed it back, I left in the
older stems, and they never recovered.  They failed to regenerate healthy
growth, and the new growth was short, with tiny leaves, looked calcium
deficient, and it died at the growing tips.  Adding calcium and boron, did
not help.  I have a test kit that tested around 80 ppm of calcium in the
water.  Those stems finally died completely. I wonder if these results
indicate that wallichii is better at extracting at least some nutrients
from the water column than it is with its roots---maybe calcium.

A very early notion in aquatic plant nutrition was that the roots of
aquatic plants served only to anchor the plant and played no role in
nutrient uptake.  This was an assuption, and it got disproved by the
experiments of a researcher named, Pond, in the early 1900's.  He showed
that floating plants did much more poorly than rooted plants.  I havn't
kept up on the literature, but I am pretty sure that both roots and shoots
are shown to be able to extract nutrients.  I do not know if there is any
concensus about certain nutrients being preferentially absorbed by roots or
shoots.  I have found that fertilizing the water column works for my
plants, and I have not counted on my substrate providing anything except

The wallichii I have now is some that I obtained at the Aquatic Gardeners
convention, last November.  I let the plants sit in their bag for almost a
week after I got back from the convention, then bleached the three-quarters
rotted plants in 5% liquid bleach for four minutes (a rather strong
treatment for such a delicate plant, but guananteed to kill hair algae). I
floated the few stem segments still showihg signs of life in a guppy tank.
Believe it or not, they recovered and sent out small plants with short
roots.  This experience makes me think that if your wallichii is about to
kick the bucket, cut the stems and float them.  They may recover!  Mine
have been floating in my guppy tank until about a week ago, when I planted
them in a newly set-up aquarium.  In the guppy tank the new growth was, in
some cases, several inches long, but didn't look healthy probably because
the plants were not rooted.  I think I want to establish at least some of
the wallichii under emersed conditions on the windowsill, so that I wont
lose it all, experimenting on it.

Paul Krombholz, in  central Mississippi, where we got less than an inch
from Allison.