I made this reactor for my yeast-based C02... This is my first ever post here, so thought i'd make myself useful!! 
It's really simple to make.. and the position of the pump inlet makes a great churning action.
What you need:
How to make the reactor:
... and in place in the tank...
.... you can just see it here in the corner of this (very poor) picture of my tank
you'll need to adjust the pump so that it's churning the CO2 at the top of chamber, but not so fast that it blows the bubbles straight out of the bottom... i find about 3/4 of the way works fine
Hope you find it useful!
It's really simple to make.. and the position of the pump inlet makes a great churning action.
What you need:
- A hagen mini gravel cleaner (for the reaction chamber)
- Aquarium silicone
- 90' airline 'elbow'
- eheim compact 300 pump
How to make the reactor:
- Seal the hole at the top of the gravel cleaner with silicone
- make a hole about 1.5" down the side of the tube - make it so that the outlet of the pump TIGHTLY fits... i made ine slightly smaller than needed and then heated the gravel cleaner in boiling water and forced the pump outlet into the hole.
- make a TINY pin hole in the gravel cleaner just ABOVE the pump inlet hole - this is so you can set the pump on a timer and at night C02 can escape the unit... when the pump is on and churning the C02 you'll find next to none escapes from this hole (as long as you make it really small and close enough to the pump inlet)
- make a small hole for the airline elbow about 2.5 from the base of the cleaner DIRECTLY underneath the hole for the pump inlet - so that the bubbles of C02 will rise into the flow of the pump
- YOU'RE DONE
... and in place in the tank...
.... you can just see it here in the corner of this (very poor) picture of my tank
you'll need to adjust the pump so that it's churning the CO2 at the top of chamber, but not so fast that it blows the bubbles straight out of the bottom... i find about 3/4 of the way works fine
Hope you find it useful!
