For calcium, you test and then wait three days with out dosing. You then see how much it drops so then you know how much your tank is consuming.
Divide the difference by three so you get the average consumption. That's how much you should dose daily.
Use this calculator to get your levels back to where you want them to be. When increasing your levels be sure to add slowly. You will need to test every once in a while to make sure your levels dont get too off. Your corals will consume more as they grow.
Both calcium (as B-Ionic) and iodine (Tropic Marin Pro-Coral Iodine) daily. I test periodically...sometimes once a week, sometimes less depending on when and how much water I change.
what are you dosing? each product is different. Usually calcium and alk are dosed daily. Iodine has daily and weekly additives.
Some people test their water every day for certain things, some do it weekly, some monthly. If you know things are stable in your tank then u can test less. You get the Pro Reef Badge when you can read your tank to tell you if the params are in range or if they are off.