Yes, I have a glass top. No, I don't have much surface movement. I hat a HOT Magnum 250 filter, and I keep the tank filled to a certain level plus point the filter outlet down just a wee bit so that it does not disturb the surface.
Also, has anyone ever encountered a situation where the check valve saved them? I was under the impression that check valves wouldn't work in a DIY CO2 system because there is pressure coming from the yeast tank, which is on the wrong end of the check valve. Anyone?
I have yet to install, or need, a check valve.