[Jacoda]

Scrap the needle wheel and use the Mag7 pump (I didn't want to mention Rio 2500 I am using :D ) for the circulation, direct the water from your overflow to the input of the skimmer or just use a small pump like Maxijet900.

When there is too much air going through the circulation pump it will cause the pump to cavitate and STOP water flow, which leads to no bubbles. Especially with the needle wheels, it doesn't take much for it to get into cavitate state.