The 1/8" tubing from UGF is what the air stone attaches too.
It is the same as the tubing found on ro units except it's rigid.
EDIT - ACTUALLY it's not. THE RO line has an inner diameter of 1/8" - the outer is bigger.
Air hose will attach to it without any problems.
Someone made a topoff with a pingpong ball and some PVC on this board. Worth a look.
I still say the $172 I spent on the Tunze system was the best money I've spent. It uses infared (sp) and doesn't let the water go down more than 1/8" of an inch. for what it's worth...
Good luck all the same. Hope that helps..
