03-01-2006, 03:56 PM
Join Date: Nov 2005
iTrader Positive Rating: 100%
Originally Posted by guaiac_boy
My understanding of the DIY CO2 reactor is that water goes downward and CO2 tries to go upward. You want the CO2 to be up at the top where it can be churned & dissolved by the water entering the reactor. Large bubbles of CO2 will rise faster than small ones according to Stokes' Law. (Big bubbles rise faster in hairgel than small ones. Large rocks sink faster than fine sand particles, etc.) Once the CO2 bubbles become small enough, their bouyant force diminishes and drag from the water current starts pulling them downward.
If you use a larger diameter pipe, the velocity of the downward flow is smaller and only very small bubbles will be carried along in the current. If the downward velocity is too high (pipe is too small) then rather large bubbles will be wasted into the tank.
Water velocity in the reactor is much faster in the center of the pipe than it is along the walls where friction slows it down considerably. If you tilt the reactor about 15 or 20 degrees from vertical, the bubbles tend to rise upward along the wall where the velocity is smaller. By doing this, only the most minute bubbles can be expelled into the tank, making for an efficient design.
I'm assuming that the filter, powerhead, or pump a person would use for a 90g tank would have a high flow rate. This would demand a larger diameter to keep downward velocities slow in the long reactor part of the design.
No matter how high I turn my needle valve, no bubbles whatsoever come out of my reactor. It's a little weird because it makes me wonder if something is wrong, but the pH is low and the CO2 is high. In fact, so high I killed a fish today. You could tell because his eyes were all bulged out. Classic signs of o2 deprivation. But, I am new to this so I am learning.