diy skimmer help

[eli@fijireefrock.com]

i have tried this.
cap the bottom of the tube have another 4" diameter placed on the inside.
water goes in to from the tank to the inner tube injecting 600gl/hr with lots of air bubbles.
at the near bottom is the outtake a 2" bull valve.
now the problem is that i am still getting lots of micro bubbles into the tank.i am at a loss.