It's just and idea, and I was wondering if someone had tried it:
Get some crushed coral (or another Calcium containing material) and put it in a container with water. Bubble CO2 in the water so the coral disolves and the water ends up rich in Calcium.
--Nikolay
Get some crushed coral (or another Calcium containing material) and put it in a container with water. Bubble CO2 in the water so the coral disolves and the water ends up rich in Calcium.
--Nikolay