you can see air and other stuff inside of silicone tubing if you have decent lighting. i am refering to the popular 1/8" wall tubing, the 1/18' is much clearer but kinks WAY to easy for my liking.
check out
http://www.procooling.com/articles/h...plumbing.shtml
for a comparison between the 2
there are some pages after that with more pics too if you need