Mt C02 levels are comming from a DIY c02 system. I made 3, two liter pop bottels hooked up with a gang valve. I bought a "ladder diffuser" from my LFS, so hopefully that will work. I plan to upgrade to presserized C02 soon, but I just don't have the money right now. What do you think about my DIY Co2 settup on my 75 gallon. Each bottel lasts about 3 weeks, so I co-ordinate changing one bottle every week. This ensures that I'll keep a constant flow of C02, and levels won't fluctuate very much. Do you think this approach will work with a 75 gallon? I read about someone else on this forum who has a 75 gallon DIY C02 with a micro bubbler for diffusing the C02. He claims that he's getting up to 25 ppm in a 75 gallon tank.