I have been using RC for the last 3 years in this way:
Weekend Water Change :25 G
After I do the WC :
-I have 1 Brute tank with 30G of RODI filtered the previous week. This RODI water is passed the mixing tank (30G Brute). To which I add RC salt.
- Then I leave it mixing (pump) + Air pump + heater, for another FULL WEEK. (in other words, till next WC).
- Now the RODI brute is empty, so immediately I start to filter water. That RODI freshly made water stays in the brute for a week until all the cycle is repeated.
In other words: I have 2 30G brutes, one with RODI and the other with RC salt water standing for a week. The salt water has a pump, air-pump and heater.
I NEVER measured the RC Alk before the WC. I only care of the tank Alk. The tank has been always between 6.5 - 8 (along all those years) with an average of 7-7.5 most of the time.
Cheers
Daniel