Re: bubbles forming during water change

> From: psears at emr1_NRCan.gc.ca (Paul Sears)
> > 
> > From: "CORBEIL, SCOTT" <corbels at macmail_mcgawpark.baxter.com>
> > Subject: Enigma
> > 
> > phosphate level is below 0.1ppm.  The weird thing is every time I do a =
> > water change I suddenly see a burst of activity in my plants, i.e. the =
> > plants release oxygen bubbles like crazy.  This, to me, indicates a =
> >
> 	The water going into the tank would be expected to have a fair
> bit of dissolved gas, if it came from a cold water main, but I wouldn't
> expect it to be enough to produce the sort of effect Kevin regularly
> saw (and still sees, Kevin?).

I get this phenomenon when I do water changes, as well.  After several
water changes, I was able to observe that the small bubbles begin to form,
if they form at all, before I begin adding the water change water.  The
only difference in the tank conditions is that the water level is now
below the output of the power heads which run the UGF.  So, I deduce that
the increased surface agitation from the powerheads has caused an increase
in the dissolved air content of the aquarium water.  Whether this air is
increasing the CO2 availability to the plants, leading to increased
photosynthesis, or whether the air is simply precipitating out on the
plants is unresolved.

This phenomenon has led to the following line of thought.  One approach to
managing CO2 availability for aquarium plants is to elevate the levels of
CO2 in the tank artificially, then limit CO2 exchange with the atmosphere
by limiting surface agitation.  This limits the depletion of CO2
availibility by the plants during the day.  In the absence of such a
strategy, we are all aware that in the relatively still water of a home
aquarium, diffusion is the only mechanism to replenish carbon dioxide,
and is woefully inadeuate for the job.  What if, on the other hand, CO2
were kept at ambient levels during the day by vigorous aeration of the
water surface?  Although not as beneficial as the elevated CO2 levels
obtained from gaseous injection, wouldn't a continually available few ppm
of CO2 give a boost to most aquarium plants?  It seems to me that the
other side of the CO2 merits some thought; i.e., is it possible to
increase the ability of plants to use the CO2 already available in it's
environment, rather than increase the CO2 availiable to the plants?  I
think both approaches get you to the same place, if they can be

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