yeah, as above, if the tube with the bubble in it is horizontal you need to tilt the case up to 45 degrees so that the "exit" of the tube is much higher than the "intake" end of that tube... follow the flow of your tubing in the direction the pump pushes the water around and you can basically force the air to keep going in the direction of your res to get rid of it
it's like one of those kids toys where you have to tilt it to get the balls in the right holes