Re: Growing certain plants without CO2

[krombhol at teclink_net (Paul Krombholz)]

    * From: "Robert H" <robertph3 at attbi_com>

.....Well if you can grow glossostigma, Rotala macrandra, Rotala wallichii,
Rotala magenta and several other stem plants, without CO2, I'd really like
to hear about it. Seriously. I have tried several time to grow glosso under
various conditions without CO2 and it just doesn't fly. In fact I am putting
together a list of plants for use with only added CO2, but before I make
that statement I would really like to know if anyone has done this
successfully......


An important consideration when growing plants "without CO2" is the various
species that you are trying to grow together.  There is wide variation in
the abilities of aquatic plants to extract CO2.  In a group, the species
with the best ability may thrive while others may languish.  "without CO2"
means without the addition of CO2 gas from some source, such as a tank or a
yeast culture.  Don't forget that fish and decaying organic matter are also
sources of CO2 which might be adequate for a certain species if it were not
in competition with other species that have better uptake abilities.
Basically, we are talking about unlimited CO2 versus limited CO2 sources.

I have been able to grow Hygrophila polysperma by itself just fine with
occasional oatmeal flakes added as a CO2 source.  But, when I had H.
polysperma in the same tank with a bunch of Ceratophyllum, the Hygrophila
completely stopped growing while the Ceratophyllum thrived.

If I were to try to grow Glossostigma, Rotala wallichii, and R. macandra
without the addition of CO2 gas, I would try to grow them alone, each by
themselves, and have fish present or have no fish, and add occasional
oatmeal flakes as a CO2 source.

With a limited CO2 supply, one may still be able to keep groupings of
species together as long as no member of the group has a distinct advantage
over the others in ability to extract CO2.  Light levels may be important.
At higher light levels, the species with lesser CO2 extraction abilities
may die out, whereas at lower light levels, they may have an advantage over
their competitors.  The amount of plants in the tank would be important,
too.  Competition for limited CO2 will not be as severe in a sparsely
planted tank as in a densely planted tank.

Paul Krombholz in foggy central Mississippi.

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