Advice with Aeration Bubbles

Just started aerating with an aquarium pump and a stone into a carboy. I've done this three times already, and the bubbles that are produced overflow out of the carboy mouth easily within 5 minutes. I was hoping to get more like 15 minutes to a half hour, but this seems to be making that impossible. Any tips on how to control these bubbles? This happens even with a good gallon or so of headspace.

If you're getting bubbles, you're pushing too much air – if it's rising to the surface, it's clearly not getting absorbed in the beer. When my oxygen kit does this, I just close the valve a bit to cut the rate I'm pushing O2 through the stone. Maybe you can do something similar, throw a C-clamp on the line or something, to restrict the airflow to the stone?

Also, if you're not doing so already, make sure the stone's really deep in there; even on the right setting, when the oxygen gets fully absorbed at depth, my O2 stone will foam when it's right at the surface; the bubbles need time to diffuse.

Thanks a lot for the tips. The stone is pretty deep, but I will try what you suggest regarding the C-clamp.