Bubbles in my display tank

[SaltSolutions1]

When I set up my fuge I ran a tube from my bulkhead into my display tank and ever since I hooked it up bubbles empty out of the tube into my display tank. Here is a pic:

Is this good or bad and what could be causing this? The bulkhead, 90, and tube are all tight.

 

[SaltSolutions1]

upper right hand corner.....red circle

 

[bolandess]

How do you have the sump set up? Is there a bubble trap before the return pump? Did you shut off the return pump before doing this? Perhaps your return pump is sucking air somehow and isn't self priming.