Well there are three main ways of introducing calcium to your tank: adding live rock which already has some coralline algae growing on it, adding scrapings of coralline algae from another tank or possibly your LFS if they would be kind enough, or purchasing a commercial coralline algae starter kit. As soon as i start noticing good growth of the purple algae on my rocks and glass walls i will take a toothbrush and gently brush the little algae pollinators so that they float around my tank and land onto other rocks to start the process ove Probably the most common/efficient way of maintaining proper calcium levels and keeping it buffered is using a limewater or kalkwasser mix (aka calcium hydroxide). you can also use a calcium additive when you do a water change such as Red Sea "Calcium Plus 3" which you would mix the proper dosing amount into your water you are adding during a water change. Be sure that anything you add you can test the levels for. you wouldnt want to add too much or too little of the amount of calcium. you will also want to get some kind of buffer for the calcium to keep it from precipitation into the water column thus making it not useable by the corals (if you have any) and the coralline algae. I myself use the Red Sea Calcium Plus 3 to add calcium everytime to everyother time i do a water change depending on the level still in the tank, however i am in the process of getting a kalkwasser setup myself. hope that helps, g'luck with your tank.
