I was fortunate to get an almost new Eheim 2227 from a friend after my Fluval 304 finally died. Even though most people would kill to get this filter for free I am now realizing that the wet/ dry function has killed my CO2 levels. I have read posts on several forums of people "turning off" the wet/dry part and leaving the filter in continuous flow while using the breather tube as a CO2 injector, but no one seems to explain how to do this and what effect this may have on the filter.