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Co2 diffusion




To respond to the thread about Co2 diffusion; I have two tanks in which I 
use Sugar/Yeast Co2.  In the 20g I use only a Hagen 201 powerhead 
attached to a sponge filter. I cut a small hole in the sponge filter and 
insert the tube from the Co2 generator into the plastic/tube core of the 
sponge filter.  This setup works best in my circumstances.  The bubbles are
chopped up and sprayed out in a fine mist of bubbles that follow the 
current around the tank before rising to the top.  I have relatively soft
(3 - 5 dh for both GH and KH  Tetra kit) alkaline water (ph of 7.5) which 
seems to dissolve Co2 well as this set up drops my PH to between 6.5 and 7.0
(Lamotte wide range) for up to a month before it begins to rise and I 
refresh the mix.  This tank has 40 watts of fluorescent light with a soil/
vermiculite/worm casting substrate and no cover.
	My 50g tank is another story.  This is a very well planted tank 
with a laterite substrate, uncovered, filtered by a Fluval 303 which I 
now understand to be way to much filtration for a plant tank but it 
provides good circulation.  The Co2 is diffused by placing the air stone 
from the Co2 generator under the intake. The problem in my circumstance 
is two fold. 1)This method is too efficient so when the generator is new 
and more Co2 is produced the Ph drops lower than I would like and 2) The 
gases produced from the genorator collect in the filter sometimes making 
god awful noises and in general (I think) degrading the effectiveness of 
the pump.  The Fluval is designed in a way that places the impeller 
assembly at the highest point in the filter and so the impeller well 
fills with Co2 and other gases making the impellar turn in a mixture of 
gas and water.  This has to slow down the impellar. 
	If I had to set this tank up again, knowing what I know about the 
ability of planted tanks to filter themselves I would use a Hagen 402 
powerhead and sponge filter and have the Co2 spray out the way it does in 
the 20g.  This is a good set up as I think it provides a good balance 
between mixture time and gas escape ability. YMMV :-))

				Yours Aquatically,

					Miles Morrissey
					Easthampton, MA