Okay, had another look at my ozonator and piping. I do have two check valves in the tubing at the top of the hot tub. I have pulled the piping off the ozonator and it can feel the suction from it. I may put that in a cup of white vinegar to clean out the tubing, check vlaves and injector.
I have found that there is a flow resrictor on the inlet of the ozonator. When I take this off the bubbles get even bigger....put the flow restrictor back on and the bubbles reduce a bit but it still seems too vigorous.