Sorry this might be a stupid question but how do I stop the bubbles coming from by Aquaclear powerhead? I have the plastic tube still hooked up, is this the problem? Should I take the tube off? By the way, if you didn't know, the tube runs to the outside of the tank and has a knob that controls the airflow. Oh yeah, one more question. Should I get the pre filter for the powerhead? Any cons to using this? And should I position the power heads to shoot "through" my live rock? Thank you for helping out this newbie.