Harry,

Forget the controllers. No need for them. I inject CO2 in the
canister intake at a rate of about 1 buble every 3-5 seconds. It's a
55 gal. tank with just 10 Amano shrimp - the CO2 is always about 15.
My KH is 4.
To me personally CO2 Difusers and especially controllers don't make
sense in a home tank.