If the bubbler was still putting out bubbles under the ice, then the
pond will be fine. That air is escaping somewhere around the
edges or some cracks in the ice. Having a hole in the middle
of the pond isn't what is important. What is important is just
having any bad gasses escape.

I had a bad experience with my bubbler last year following that line of
thought - it is true that as long as you're bubbler is making bubbles under
the ice, the air must be escaping along the edge somewhere, but your ice
dome is getting thicker as long as the temps stay cold enough
I got lazy last year and let the ice dome stay froze over for 3 days and
the ice kept getting thicker - when I finally went to break it (light
tapping works OK on thin ice, but needs to be done daily or twice a day on
real cold days ) it was 2" thick and I had to use a cordless drill with a
spade bit to make 1" holes in it - they froze over in no time and eventually
the ice froze down to the airstone, freezing it up and killing the air flow
and I had to borrow a 1500 watt stock tank heater and let it melt it's way
through the ice to open up a hole - from now on I am going to check the hole
to make sure it isn't froze over as it only takes a minute to grab the stick
to tap the dome and break it open
Gale :~)