My new toy....need some help

[Tarolisol]

Ok now I probly have a couple dumb questions. First, do i fill both chambers with media, and second i assume the valve is what i use to control the speed of water exits the reactor into the tank but wouldnt closing this cause to much pressure in teh reactor or on the pump? Also I do i know if im using to much CO2, does that equal to much calcium? And finaly, if turning down the Co2 causes calcium levels to drop what is the purpose of the valve.

I hope all these questions make sence.