How to control PH at night ?

[Casey8]

I have a problem to keep PH at night. I have been trying to drip Kalwasser, it really helps the PH not to drop too low, I can say it is almost perfect like in the day time. But the problem is, my KH is getting to high if I dose every night. I mix 5 table spoons in 5 gallons and keep filling it up with water for another 3 to 4 days maximum. I threw away the left over at the bottom. How do you guys control your PH not to drop at night ?