Ok I setup my brand new Fluval 104 tonight. I read other threads about getting the air bubbles out, etc. Well it has been running but even after having it run for nearly 15minutes I can shake it and cause it to do this "woosh" sound of airbubbles into the tank. Is this normal and could it be caused from a crack/non-solid connection from my tubing? I have rigged up a DIY CO2 on the input but I have shut the valve until I can figure out the cause of the bubbles.