Kamon

I have an AquaClear HOB filter on my 29gal that I've been using for nearly eight months. The filter works well, but its been posted on APC and other forums that HOB filters can lower the level of CO2 in a tank. Water level in my aquarium is level with the filter to reduce this effect. Canister filters sound much better, but I'm a bit short on cash atm. Any cheap canisters out there (DIY works as well)?

DIY yeast CO2 is decent at best. I'd rather have a pressurized system. A paintball CO2 tank sounds affordable. I have no experience with pressurized CO2, so a good explanation of what all I would need (while keeping things cheap) would be great.

Thanks for reading.