[jmontee]

There is some info missing to get a good answer for this question. What are you using to diffuse the CO2 into the water? The more effecient the system the lower the bubble rate you will need. If you are using a reactor then o.5 to 1.o bps should be enough as this is very efficient. Although the bps thing is not always very accurate due to different bubble sizes from different needle valves.

The drop checker is your most important tool in regulating the CO2 in the tank. Are you using 4dkH reference solution in your drop checker? If you are using just tank water then it may throw off the pH in the solution due to other substances in the water.

The best thing to do is start with a bps that you feel is good for the method that you are using and within 2 hours you will be pretty close to the saturation point that can be reached in your tank. Watch it for the day and adjust as needed. I wouldn't worry a lot about the fish as you will need to seriously over dose CO2 in order to kill them before they start to show signs of being uncomfortable.

 

[jmontee]

They can be slightly less efficient. In a CO2 reactor the bubble of CO2 gets mixed around in the water flow and has no choice but to dissolve. Using the ceramic disc there will be some bubbles that will get to the surface and go into the air. One thing that will hep is to put the diffuser right next to your intake and this will use your canister filter as an extra means of diffusion. You can also make sure that the stream of bubbles is put out under the spray bar where the flow from the bar will spread the tiny bubbles all over the aquarium giving them more time to dissolve.

Either way it sounds like at 1.5 bps you are keeping everything in line.

One way of maintaining your bubble count is to make sure that the secondary gauge is up to 20. I have the same regulator and for some reason it really needs to have a higher working pressure than other regulators. Then use the needle valve on the bubble counter to get the rate that you want.

 

[jmontee]

I would just leave it on. Give your solenoid a break from having to go on and off twice.