When I put my check valve on my air line the air doesn't come through the air stone but when I take off the check valve it works. Also I switched the sides of the check valve and it didn't work. Click the link this is the air pump.
Or if you can, go to petsmart and get one there. Petco tends to sell sub-par items and livestock. If you have a tank that is bigger than your air pump was intended, then you will have problems. Say you bought a 10 gallon air pump for your 20 gallon tank. The strength of the pump is only able to push air down to counteract the average depth of a 10 gallon tank, against the pressure of only that much water. However if it were in a 20 gallon, it may not be able to counteract the water and the check valve (which shouldn't be causing much of a problem anyways). Make your line shorter and see if that helps. You don't need tons of extra airline tubing coiled around. Cut it down to the length you need, and try again. Remember, check valve should be OUTSIDE of the water, in the direction indicated on the valve (as to which side is in, which side is out), and it should be closer towards the pump itself. The check valve just prevents any water from dripping back into the pump.
