i use calcium chloride from dowflake though purity has recently become an issue. tetra has a calcium chloride product. dose in a high flow area but away from power heads and heat sources.
well my water volume is about 220 gal and it is a medium stock but i run kalk and i dose calcium and alk in a 2 part recipe. but i would say you can start with a 1/4 cup of both and see where your levels are.
also make sure you check alk more often as it fluctuates more often then calcium.