One of two FX5s shooting out tiny bubbles

[brcacti]

one of my FX5s is shooting out some tiny bubbles with the water, any thoughts on what it is, why?

 

[nfored]

I know its a different canister but my fluval 403 did that when I had a small air leak in the return line. Right at the bottom of the U before the spray bar air was getting sucked in.

 

[OnceLoyal]

I just bumped a really old post on this that seemed to have some good info. I will try everything either tonight or on Mon. The only thing I will have a problem with is keeping the intake 4ft from any return. The tank is only 6Ft with overflows on both sides