"floguru" wrote:
Forgive me for being controversial but I have drawn the following
conclusions on CO2 injection.
Question - are you basing your conclusions on guesswork, or have you
actually used CO2 injection?
CO2 injection I can only summise has one achievement, to increase the
acidity of an aquarium and thankfully not as effectively as it could.
The increasing acidity demonstrates quite clearly that CO2 injection
is working, and achieving the result of CO2 gas being dissolved into
the water.
If I use an air pump and the % make up of atmospheric air is .036% CO2, a
100 litre per hour air pump (very small) is going to deliver .036 of a litre
of CO2 into my tank every hour its working. That equates to 1 litre a day or
100000 milligrams of CO2 a day. Now aquatic plants only need about 30
milligrams of CO2 per litre of water so I have delivered 33 times more CO2
(based on a 100 litre tank) than they need.
Now here's the kicker. Most of the bubbles go straight to the surface and
take the CO2 with them
Correct, the bubbles from an air pump leave the tank, and so you're
*not* delivering 33 times more CO2 than needed. Everything I've read
(apart from sales babble) indicates that bubbles from an air pump have
little if any direct effect upon dissolved gasses in the water. In
other words, don't consider air pumps at all when you're contemplating
CO2 injection, as they're totally unrelated.
CO2 injection usually involves a reactor of some sort, be it a simple
bell or a powered chamber. I'm using a Hagen diffuser with DIY,
generally delivering one bubble per second of CO2 gas into the
diffuser. Virtually all of that is dissolved into the water, with only
extremely tiny bubbles occasionally leaving the diffuser.
So, unlike the air pump case you present, the vast majority of the CO2
in my system is being dissolving into the water, and not directly
escaping in the form of bubbles.
I would be interested in wheither anyone has actually measured an increase
in dissolved CO2 before and after injection and the corresponding effect on
pH.
Most people doing CO2 injection have, though we work the equation in
the other direction. If you know the water hardness and pH, you can
calculate the CO2 level.
You can find the formula and a handy calculator at Chuck's page:
http://www.csd.net/~cgadd/aqua/art_plant_co2chart.htm
By this formula, my CO2 level without injection was typically about
2.6 ppm. Once I got my CO2 injection working, that level rose to and
stays in the mid-teens. With new DIY bottles, CO2 will on occasion
rise as high as 30ppm (DIY isn't as stable over time as bottled CO2
injection, unfortunately).
So yes, we can and do actually measure an increase in dissolved CO2
when using CO2 injection.
--
www.ericschreiber.com