Join Date: Sep 2003
Location: San Francisco, CA
My tank is about three and a half gallons, a Mini-S. The smaller of the two diffusers is about half an inch in diameter.
As for cleaning and maintenance of a glass diffuser, it depends on how clean your tank is. Not too long ago, I had an algae outbreak and the thing got debris and algae on it quite regularly. I've gotten the outbreak under control and now I don't have to fuss with it at all.
Assuming your lines are tight from the bottle to the diffuser and that your mixture is fresh, you will have no problem keeping the bubbles small.
BTW, I've gotten the cheaper diffusers and they didn't break the CO2 into consistently small bubbles the way the ADA stuff does. Anecdotal evidence, sure, but that's my experience with the cheaper ones.