Strange Filter Behaviour

[alanchown]

Towards the end of every evening my external filter (Eheim 2126) starts chucking out loads of air bubbles. It's perfectly OK all day, then all of a sudden out come a load of fine bubbles.
I have no idea where this air is coming from, but is it possible it is a result of my plants pearling, my Riccia is covered in bubbles in the evening-could this oxygen be making it's way into the filter?
If not any ideas where it's coming from?

ALan

 

[Puffer punk]

try giving it a very good shake its prob a air lock from when u 1st set the filter up

 

[Themuleous]

Do you run the CO2 into it that can do the same thing, or so Ive heard

 

[alanchown]

Do you run the CO2 into it that can do the same thing, or so Ive heard

Nope