I am using a KI (Key Instruments) Air Flow Meter (5 to 150 scfh) to measure the air-pull on my Orca 250 Pro. I can't get more than 35 scfh which is around 1000 lph, around 50% of what this skimmer is claimed to achieve (70 scfh ~ 2000 lph). Any ideas on how I can get greater air-pull?