I heard that 1tsp per gallon Is a good amount of kalk to use, but I need to know if the 1 tsp / gallon means per gallon of the entire tank system or per gallon of makeup water?
I would imagine that 1.25g of Kalk would be just a sniffle under a heaped teaspoon. Not that im an expert on weights and measures, especially when it comes to white powders. If i get the chance ill get some out on my Digi's and have a look.
Besides anything else, any Kalk that has not been absorbed by the water will just settle on the bottom anyhow. You can even use it to make up fresh kalk, just add more water and give it another stirr. I usually only re-use settled kalk over a pereod of about two weeks.