In a message dated 8/6/01 4:25:25 PM Eastern Daylight Time, Aquatic-Plants-Owner at ActWin_com writes: << 1. If you are using a wet-dry filter on a CO2 injected tank, and you left the wet-dry open to the room air, you would lose most of your CO2. >> That's exactly what I do - yet I have no shortage of CO2 in my tank. Even if I did, I'd just turn up the CO2... Bob Olesen