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Re:CO2 at lower lighting

    * From: Thomas Barr <tcbiii at earthlink_net>

> > When Klaus Christensen (Tripica, DK) visited us a couple of years ago he
> > insisted that the most beneficial thing one could to to a planted
> > aquarium, even a low light one, was to introduce CO2.

> I agree and have independently found this to be true from a practical
> standpoint.

> > Klaus was adamant
> > that CO2 was more beneficial then additional light or other nutirents.

> Again, I agree.

> > That said, one can achieve the balance at almost any light level,
> > although without CO2 it's far easier at lower levels.

> Again, I agree. Folks seem to buy the lights first, then get iron and
> nutrients next, then they fight , kick, scream and whine to no end about not
> using CO2, or getting around it. I'm always amazed at the reasons folks do
> not get CO2 or do not want to use it but have no problem rationalizing a
> 100-400$ lighting PC set up when the NO T-8's and T-12s work although
> bigger. I agree that CO2 is the single best thing for helping a plant tank
> in most cases.

The article by Ole Pedersen, Claus Christensen, and Troels Andersen in TAG
14, #1, makes the same point and gives results with Riccia that support the
point.  However, I recall one experience where pushing CO2 caused prolonged
and severe melting in Cryptoryne wendtii and C. cordata in a very low light
tank---a 29 gallon with one 20 watt T-12 flourescent bulb.  When I stopped
the CO2 additions, the plants recovered, and when I increased the lights to
three 20 watt bulbs, and started up the CO2 again, there was a slight bit
of melting and then the plants took off and grew rapidly, packing the tank.
According to the charts, I probably had 30 to 40 ppm CO2 in the tank, and
the light level was less than 1 watt per gallon.  The melting began after
about 4 days of the high CO2 and persisted until nearly all the leaves were
gone.  After I removed the CO2 source, the plants recovered to their
original sizes and density (scattered) in about 4 months.  Then I put a
3-20 watt bulb unit on top of the tank and started up the CO2 again.  This
time only a few of the oldest leaves melted, and then the plants started
growing rapidly.

Conclusion:  Be cautious  pushing CO2 to high levels with submersed Crypts
at very low light levels.

Paul Krombholz in chilly, cloudy central Mississippi, with the possibility
of a sprinkle today.