Air in fuel line. Problem? Help! 2002 Golf TDI

I did my first oil change today being meticulously careful to do everthing right. As I took off the top engine cover I noticed a clear plastic hose line and a black plastic hose line running to the engine from a black metal cylindrical case with for in/outs. The color of the fluid in the clear line is slightly tinted green, but fairly clear. This is the feul filter and fuel lines I figured. But I noticed a sizable air bubble in the clear line. Didn't think it was a problem. After finishing the oil change I started the car up. Now I can see lots and lots of tiny air bubbles racing thru that feul line. Now this I don't like. Is this normal? Big problem? Little problem? Suggestions?

The little bubbles aren't gonna cause any problems. They get whacked by the extremely high pressures. If they bother you, you can get rid of most of them by removing the T-fitting on the filter and filling it with diesel or additive.

The consesus seems to be that a certain amount of air is normal and not a problem. Large amounts of air and or foaming is a problem. The drain valve on the bottom of my fuel filter (the four ins and outs) sheared off allowing fuel to drain out of the filter and air to be introduced, and eventually causing the motor to quit! But that manifested its self as a lot of air in the line and noticable foaming.

Little bubbles are normal at idle. They should disappear as RPMs increase.

Tiiiiiny Bubbles!

In my liiiiine!

Make me feel Happy!

Make me feel Fiiiine!

[sorry, couldn't help it... ]

There's no foaming, just tiny little bubbles going by. I figured air must be getting in from somewhere, like an improper or loose fitting. But if small amounts of air in the feul line are OK, I won't worry about it.