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Re: Biowheels-CO2-plants redux

Dan asked about the effects of biowheels on CO2 loss.

Since the recommended 15 ppm CO2 level is more than would "normally" be
found in solution (3-5 ppm?), CO2 injection creates a temporarily elevated
number of CO2 molecules in the water.  The "excess" CO2 molecules "want" to
leave the water (beats the hell out of me why, maybe they feel persecuted
for their religious beliefs) and do so by re-entering the atmosphere at the
water-air interface.  Any time you increase the water-air interface area you
increase the opportunity for this gas exchange.  This is why low surface
turbulence is recommended - to decrease the surface area of the water
exposed to air, and to slow down the rate at which the CO2 molecules are
brought to the surface.  A biowheel creates a relatively large water-air
interface which provides the opportunity for the "excess" CO2 molecules to
leave the water and become airborne.  So, in short, biowheels defeat CO2
injection by providing a pathway for the injected CO2 molecules to leave the
water quickly.  Unless you are keeping a high fish load, or can't keep the
plants growing, the plants are a better filter than the bacteria on the
biowheels anyway.  IMHO, FWIW, YMMV...etceteras.