> From: Marty Durkin <durkin at stsci_edu>
> If I shake the solution, I get lots of bubbles in the tank.  However, if
> the solution just sits there, I don't get any bubbles at all.  The aquarium
> is in the family room in my basement where the room temperature is about
> 68 degrees.  

You probably have leaks in the gluing of the PVC tubing into your
fermentation bottle. This will bleed off pressure that is needed to
push the gasses down the tube against hydrostatic pressure and out
through the airstone which has considerable resistance too. Try blowing
hard into the outlet to check for leaks. Airstones are very inefficient
at dissolving CO2; you can use the air injection port which is on many 
powerheads. The powerhead also generates under surface currents which
help CO2 diffuse through the surface boundary layer of plant leaves
and which greatly improves their ability to absorb it.

On the subject of antibiotics:

I'm against their use in aquariums (even as a "last" resort). Their
presence in the environment contributes to all sorts of bacteria
aside from the ones which you are interested in eliminating becoming
resistant to antibiotics. That is not good. They also interfere
with the "natural" micro-biology of the tank and substrate which
is important for the uptake and metabolism of nutrients. There are
simple methods for dealing with algae without resorting to antibiotics.

The answer to life's problems does not come in a pill. ;-)

Steve in Vancouver