re: CO2 injection

---------- Forwarded message ----------
Date: Fri, 06 Sep 1996 11:09:44 -0500 (EST)
From: DIONIGI MALADORNO <MALADORD%A1%RNISD0 at mr_nut.roche.com>
Subject: CO2 injection
To: AQUATIC PLANTS <Aquatic-Plants at ActWin_com>

"John Chumley" <denjoh at ccse_net> wrote:

<<<<<<Subject: PLANT CO2 & LIGHTING

First. I am using the yeast co2 method now, but plan on moving up to a
bottle system soon.  What is the best way to disolve the co2 in the water. 
I have a 75g tank with an Emporer 400, and will be purchasing a Magnum 350
canister soon.  Should I release the co2 into the tank, the emporer or the
magnum, and how? >>>>>>

If you have available the filter outflow tube with the supplementary outlet
for the attachment of a biowheel, you can use the following system, which I
have recently used for a new tank with a HOT filter. It's just one of the
various possible solutions available:

get a 10 inch long lift tube for undergravel filters (UGF), and the end
attachment (shaped like and L) which directs the water horizontally. This
attachment should have a little hole on the top, originally designed for the
airstone line that powers the UGF. Run an airline supplying the CO2 though
it, and have the end of the airline long enough to penetrate 6-7 inches into
the tube. The tube should have first been  loosely filled with some material
that can hold the CO2 bubbles: I used the small lava rock chips sold for
indoor plant pots. You then have to figure how to connect the open end of
the tube to the filter outlet for the biowheel: I used an elbow connector I
had, but other solutions, such as flexible tubing of adequate diameter,
would be fine. It is important to use only the biowheel part of the filter's
outflow, since a strong current in the reactor would blow the CO2 out right
the way. This diffuser is installed with the end where the airline enters
directed towards the bottom of the tank (you can direct the water flow
wherever you want), and the extremity where the water outflow comes in
directed towards the top. I used some heater suction cups to hold it in
position, and some rubber bands to keep the airline in position.

Disadvantages of the system: it takes a little work to set it up (approx.
1/2 hour for me). I used spare parts I had available, but if you do not have
the components there might be also a little cost (5$ or so I guess).

Advantages: this system dissolves almost all the CO2 introduced, unless you
have a CO2 flow higher than its solubility rate (eventually some bubbles
will be blown out in this case, and you know you need to adjust the flow).
My impression with bubbles being aspirated by external box filters is that
it is difficult to see how much CO2 is dissolved and how much just bubbles
out of the filter's lid (however, many people are reporting good resuts with
this simple solution). Canister filters do not leak out CO2, but you can't
see if the CO2 accumulates in some low-flow area inside it, which is a
problem reported by some (others did not have this problem). 
Some additional biofiltration is also provided by the lava chips. You also
split the filter's outflow, distributing it more evenly. The CO2-enriched
water goes at the bottom of the tank, rather than close to the surface where
it is dispersed in the air. Most of all, it was fun to build it.