Re: Airstone anathema

To suggest that airstones are somehow 'bad' for aquatic plants is wrong, 
wrong, wrong (to repeat a recent post)! There is clear research which 
indicates that photosynthetic rates in aquatic plants increase with 
increased rates of aeration ... the reason is that increased aeration 
increases water movement and therefore decreases the thickness of the 
boundary layer. It is this boundary layer which is the limiting step in 
CO2 acquisition so the thinner it gets, the faster the uptake of CO2.
Airstones also do not 'drive' off CO2 ... they will equilibrate all the 
gases in the tank to atmospheric levels, nothing more, nothing less. This 
idea likely got started by proponents of CO2 injection who couldnt stand 
to see their CO2 levels drop even slightly ... in fact in most cases CO2 
injection is unnecessary. There are only two instances where it is 
beneficial ... the first is when there is a daily fluctuation in pH which 
indicates that the demand for CO2 by the plants exceeds the abil
ity of the water to absorb it (of course in this case aeration will also 
work) ... the second is when growing plants which are unable to utilize 
bicarbonate (about half of aquatic plants have this ability).