Air Bubble In Aquaclear Mini Filter

[KCB]

I have a large air bubble in the U-bend of my aquaclear mini filter and can't seem to figure out how to shift it, any ideas? I need to fix it today as I'm away tomorrow and the flow of the filter is half of what it usually is .
 
Thank you.

 

[Mikey1]

try adjusting the flow from max to min, then back to max again,
 
do this rapidly a few times in a row and the bubble should come out

 

[KCB]

No luck with that I'm afraid, but thank you anyway. I wiggled the tube up and down and I've managed to get the bubble towards the end of the U-bend but can't get it to budge any further than that.