mmmmmmmmmm...idk...obvioulsy the more o2 the better but if he is going up , popping then coming back down it may not be the 02 or a problem. when my angels r distressed they stay at the top and gulp not go up and down. there was a thread about this on the old forum and many had noted a popping sound form their angels so i am not sure it is cause for concern. i would be more concerned if they all were doing it. you have more agitation than my angels have.