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RE: Aquatic Plants Digest V5 #379

Jerry Said:
I have a DIY reactor made from a gravel-vac tube, some bioballs, and a
powerhead. For a long time a bubble rate of about 1/sec. was enough to
keep my pH at 6.7 with a KH at 3 (25ppm CO2). All of the sudden, my pH
went up to 7.2 the other day. I added nothing to the tank except the
usual NO3, PO4, and traces. I turned up the bubble rate to 2/sec., and
my pH only went to 7.1. I retested the KH and it is still 3. I double
checked the flow in the reactor to make sure that was fine and
everything looks ok. The CO2 tank is still quite full (reporting 800psi)

Jeff Replies:

Jerry -  I have experienced a very similar problem with the DIY CO2 reactor
I built (See http://home1.gte.net/bodin1/CO2.htm) that is somewhat based on
several of the DIY designs on the web. Check to see if there is a huge
hurricane/vortex of CO2 in the chamber, as this may be your problem...

Many of the Pictures of these DIY designs I see in operation display this
massive "vortex" of CO2 flowing/hurricaning within the chamber. Based on my
experience I think this is not optimal operation. Whenever I have a huge
vortex of CO2 in the chamber the pH goes from 6.6/6.8 to 7.4 in less than a
day, telling me that the CO2 is not dissolving into the water column as it

IME CO2 dissolves more efficiently when a vortex is not present (when lots
of small bubbles are gracefully spinning around in the chamber). Not sure
why, but this is what/how my set-up operates. Whenever I have the vortex -
no/very little CO2 dissolves.

I used to think that too much water going through the chamber would cause
the vortex (as I state on the web-page), later I realized that it was when
the input of my powerhead became clogged with a dead leaf (or something
else) that the flow of water through the chamber would slow down and then
CO2 vortex would start to accumulate, and the pH would then rise.

anyway, I hope that this was able to help you...

- Jeff