7.8 to 8.2, sorry man I didn't realise, panic. I think you need to get down and collect some water right now or most of the tank inhabitants will die. Or you could go back to bed.
Its only Kalk. I've poured it in when killing Aipstaisa, the water has been frosty white. I've used like 1 CUP full in the tank (my old 700 litre system). The result, lots of deal Aipstaisa.
Kalk binds copper too. You might notice and improvement.
Chim - All the sillyness aside, you have 0 to worry about. Go to bed, pieman garantee all will be well. Storm in a tea cup.
Pie