If you are spending around R2k per month on supplements, then buy a calcium reactor...some in the for sale section.
Just make sure when you use a calcium reactor you have a reliable way of feeding the calcium reactor to get a constant drip rate...
Kalk is very good but i wiped out my whole tank due to ato pump getting stuck in the on position and the rest was history...
A calcium reactor is the way to go imho, just needs a bit of your time in the beginning to setup and find the sweetspot.After that, kh and ca problems will be a thing of the past.