The media color doesn't change much. I use BRS media and have never really seen it change, though I do see the color change on top of the container in which I keep the media. I believe RKPeterson gave me the link for the solenoid on amazon, and it work great. Most solenoid have to keep power on to maintain a certain position, the one I use has a limit switch, so the power is turned off after the solenoid reaches the open or closed position, thus it doesn't burn out. Don't forget what I said about adding some water daily to the media. It does dry out rather quickly and shortly their after it stops doing what it is intended to so. I can see when I forget to add water to the container on my Apex as the PH drops. When I add water I am able to extend the life of the media.The air comes from the skimmer cup to the scrubber, then back to the skimmer input. I actually have to empty the bottom of the scrubber every few days because the bottom section completely fills with water.
I'm actually going to add a water trap before the scrubber here shortly so it can hold more water, and I can remove the water easily without taking out the scrubber all the time. I'm also going to add a second chamber so I can swap out the media one at a time.
So far it hasn't raised my pH enough to control it, but yeah, I might add a solenoid at some point. I already have a Tee hooked up with a 3/8" ball valve so I can let in some outside air in the mix...but haven't needed it yet for the same reason.
It might be the media, as I am currently using the bag that came with the Ice Cap Scrubber, which is supposed to change color. However, after two weeks not one single piece of it has changed in the slightest. I also bought a bag of BRS color changing media, which I haven't opened yet...so it may be about time to try that out...
This is the solenoid I use.