bubbles per minute

[Boba]

posted this the other day and unfortunately- no response. Trying again out of desperation. Set up my new Coralhound dual calcium reactor the other day but have been unable to get the bubble count stabilized. I have an Air Products dual stage regulator with a Nupro 4BMG metering valve (both very high quality). I have tried varying the pressure from 5-25 psi with correspnding adj. to the needle valve but the bubble count fluctuates by as much as 15 bubbles per minute. Any experts out there??? Thanks!