I'm not really up on Ca
reactors, but I *thought* that folks that ran them suffered from low pH if the reactor wasn't "tuned" right. I'd probably focus on that aspect versus adding something to boost your pH. Or looking at ways to improve the gas exchange. To me that just seems like a bandaid, and doesn't focus on the cure. In addition, I think by raising your pH chemically, you'll end up shifting your alkalinity/calcium parameters and you'll be chasing your tail with the reactor again.
Sorry... doesn't answer your original question for a recipe, but I guess I just wanted to suggest taking a step back and thinking whether you wanted to go down that road.