calcium reactor help wanted

What are you using for a feed pump? What are you using to control the effluent output? If I remember right the circulation pump usually does make noise when the C02 bubbles run through the impeller.
I had a hell of a time getting mine adjusted and stable at first. It didn't seem that I could get the pressure regulator to hold, and a steady bubble count through the stupid needle valve. I eventually bought an aquariumplants electronic regulator. That thing made life a ton easier and would remain rock solid even as the pressure in the bottle decreased. I had it hooked through the apex to monitor pH level and control if needed but it was stable enough the apex almost never had to kick it off.

I agree with making very small adjustments then waiting and monitoring for 24 hours to see the results.

 

10 drips a minute seems really low for the effluent. Mine was at a fast constant drip, just under the point of being a steady stream and I had my CO2 set to 1 bubble every 2 or 3 seconds. And this was in a big dual camber reef octo reactor. It really didn't take much of an increase in CO2 to see the pH drop in the chamber.
I would double check your pH probe to make sure its not giving you a false reading. Also make sure you're not losing CO2 somewhere before going into the reactor.

 

It should take what seems like very little CO2 to lower the pH in these reactors. When I was tuning mine in I could increase the bubble count to about a bubble/sec maybe a little faster and watch the pH start dropping relatively quickly. Once I got close to target I would back it off and see how it stabilized.

I would set your effluent output first. Get it so it is a very fast drip. 1 drip/sec or so maybe even a little more. Then start adjusting the Co2 to hit your desired pH. Regulator pressure as well as the bubble count will effect it. If it seems like you really have to crank to bubble count up, you may try adding a little more pressure.
I never was able to get anything that I would call stable with the standard regulator and needle valve. I fought it for weeks before i ditched it for the aquarium plants electronic regulator.

 

http://www.aquariumplants.com/CarbonDoser_Electronic_Co2_Regulator_p/co2.htm

 

You probably have an electronic solenoid valve. It doesn't actually do anything more than an on/off. The needle valve and regulator pressure is what is controlling the amount of co2.
The aquarium plants regulator is just a high speed electronic solenoid. Capable of switching fast enough to just meter a small amount of CO2.
Sounds like you have the same struggle I had when I first started with the Ca reactor. Fighting the regulator and needle valve.