If the bubbles are already showing in the tubing right after the tank, you may want to try these:
http://www.dreamworksrc.com/catalog/Fuel-Line-Barb-532

It seems from the pictures you have a brass tube and PU hose on it, without any kind of barb.
The problem could be there, or inside the tank on the pickup line.

If the UAT is sucked in, then you probably need a more rigid one