Return line is producing bubbles?

[mordred]

How can the return line from my pump shoot bubbles into my tank. It's like I have an aerator stone or something.

I checked the sump and its clear of bubbles and if there were they would have to make it through the sponge filter on my Mag 7. I also checked the connection on my vinyl tubing where it meets the spray arm for my tank. Its not leaking and still has the hose clamp tight on it.

So where is this air coming in?

 

[BillD]

Air usually enters on the suction side of the pump. If there are any bubbles caused by water cascading into the sump, that could be sucked into the pump, they would be broken into smaller bubbles by the pump. This could possibly be what is happening here.