i have had this skimmer on my brand new tank for 3 months now and can't keep it consistant. it either overflows the cup or skims nothing. i am just adjusting by turning the valve enough to feel it move(very small increments). it is in just over 7" of water and that never changes. i try to give it at least 4-6 hours between adjustments but i am constantly messing with it. any ideas? would running an air tube from the air intake to outside of the stand help any?