[blanden.adam]

Originally Posted by tmz

Hello Adam,

This is a nine year old thread;time flies.

Some comments follow in an effort to clarify things for those intersted in more detail.


I agree there is no fixed amount of dissolved gas in a reef tank or in various locations in seawater in the oceans either. Also the concentrations in water vary from those in the atmosphere, generally. Dissolved gases in sea water(nitrogen, oxygen,argon,CO2, hydrogen sulfide, methane et alia vary in proportion and overall concentrations calculated based on gas laws ,such as Henry's law. .Variables like: salinity,depth,temperature and atmospheric concentrations affect the amount of total
and individual dissolved gases in the water.

For perspective ,atmospheric levels are; around 78% nitrogen, 21% oxygen, 10% argon and only .04%( 400ppm) CO2. The water equilibrates to a large extent with the surrounding air at the surface .
In a home or fish tank room the CO2 can easily be 800ppm or even more than twice the amount in the atmoshpere.

As more CO2 hydrolizes , coverts to CO3 and 2 H+( CO2+H2O------>CO3 +2H+), it adds more H+ which lowers the pH. So, lessening the amount of CO2 in the air going into the tank continuously, raises the pH. That can be accomplished with outside air for the room , an outside airline to an aeration device like a skimmer and/ or a CO2 scrubbing device. Increasing the water surface area via the skimmer bubbles and/or surface agitation increase the rate of gas exchange between the tank water and the surrounding air.

Using kalk/lime water( calcium hydroxide Ca (OH)2 slowly and continuously will also continuously reduce the CO2 in water tank water as the oxide forms CO3 by binding with CO2.

I also agree that oxygen has nothing to do with pH and won't raise it or effect CO2 levels ,directly; CO2 independently drives it down and CO2's major source is the surrounding air.

Hi Tom,

Geeze. I didn't even notice. It popped up top because of the article article post prior to mine, and i didn't even think to check previous dates. Sincerest apologies.