I would never run any loop
I also want to know the amount of CO2 in my water, very interesting. As you have seen it is heavily related to Fresh Air Exchange (FAE) (anyone grown mushrooms before hehe). Which is probably related to the amount of CO2 in the air. I think we are right on board with exactly the same ideals, glad your tank is doing so well, my tanks not worthy!
Wow Dennis nice find again