I've had DIY CO2 going for about that long, but it was on small tanks so a little CO2 went a long way.
A couple other tricks - put the heater on with your light timer. It will lower production during the night, when it's not needed.
Another easy way to increase CO2 production is to simply add a 2nd bottle. Then change them out at different times to help keep production level. 2 week cycle, change one every week. Stretch it out to 3 weeks or more of you want.
Last edited by csf; 01-30-2006 at 01:09 PM..