That's funny that you mention that... Although I like the looks of my UP Aqua glass diffuser, it does put out larger bubbles than my (cheaper) Fluval ceramic diffuser in my other tank. I think the UP Aqua is just another cheap-O knock-off (like the no branders), that decided to brand themselves. Even so the bubbles are larger (especially at lower bps rates), my drop checker is still a nice lime green. I think the seal between the ceramic disk and the glass is not really tight... because that's where the majority of the larger bubbles emanate from. Glad I got the drop checker though, now I can monitor how much co2 is actually getting diffused. I borrowed my other one for a little bit and after a few days I removed it (once I got the bps rate dialed in). But by re-adding the drop checker, I discovered I actually had to reduce my bubble rate a bit because it was getting boarder line yellowish (which I didn't even know... obviously).