Cheap way to make supplements
Calcium - Two cups of driveway heat/calcium chloride into a one gallon bucket and your solution is ready. For detailed information and calcium recipe I suggest you go reefkeeping.com. This site is awesome and has step by step instruction on DIY supplements.
Magnesium - Pure Epsom Salt from the Grocery store. For detailed information and magnesium recipe I suggest you go reefkeeping.com.
Kalkwasser - One tsp of Ms. Wages pickling lime to about a gallon of water and let it drip into your sump over night.