Some might be interested in this.
I've implemented CO2 scrubbing, but after some experimentation and testing, have decided only to do it at night to 1. stabilize pH, 2. not let pH get too high during the day, 3. keep alk from dropping excessively, and 4. leave plenty of CO2 for photosynthesis and skeletal growth during the daylight hours. At first I would insert and remove the scrubber hose into the skimmer aspirator manually in the evening and morning, respectively, but this got old quick. At first I thought of setting up a bypass with a solenoid and controlling this through an Apex outlet, but the problem with using a solenoid here is that the open and closed durations are long and of similar length; so any solenoid would need to be energized (and getting hot) for far longer than I would consider safe.
Instead of a solenoid, I eventually found this
motorized valve. This thing is great. Plug it into an AC outlet (or turn the outlet ON), and a motor turns a ball valve 90 degrees over a few seconds to obstruct the flow, and then turns the motor off, latching in place. It will stay that way until you unplug it from the AC outlet (or turn the outlet OFF), when the device detects the loss of power and opens the valve.
Here's how I have it rigged under my sump. The valve is at the upper left, with a hose directed to the right. The hose from the CO2 scrubber is coming from the upper right toward the left. A black T in the upper back connects the two, with a hose coming down and forward from this to attach to the skimmer. Apex turns the valve's outlet ON, the valve turns to block the flow of air, and all the skimmer air passes through the scrubber first. Apex turns the valves' outlet OFF, the valve turns to allow the flow of air, and all air now uses the shorter lower resistance route through the valve, with no CO2 scrubbing.
