I've had this inline FE CO2 setup for about two and a half years now, and it has been easy to use with good results. Sometimes there is a build up of gas at the top, so I bleed it with the small tap to restore the water level. Today though I cleaned the XP3 filter that feeds the reactor, just like every other time, but tonight I found the bubbles are being trapped at the bottom mixing into one big bubble. I tried bleeding it, but the water level is already at the top. The only other thing I can think of is the sponge/alfagrog insert is dirty and is stopping the bubbles travelling to the top. If so, I need to find a way of cleaning the sponge without flooding the carpet ! I think the top MAY screw off, but then I'm going to worry if it goes on tight enough again. Has anyone done it already ?