Bubble size is an easy way to tell if your spa's ozone system is properly getting ozone into the water where it does it work.  You want champagne-like bubbles popping on the surface of your spa water, not bubbles that gurgle. 

Big bubbles indicates your ozone's not in the water where you want it.  Rather, its off-gasses which can break down your spa pillows and cover faster.

By restricting the flow through your ozonator, you increase the ozone saturation and, as a result, get the most chemical reduction and the best spa water imaginable.  Awesome!.