Yeah, mcbdz has it right, only add what you can test for. You can not test for iodine or strontium. You honestly really don't need it.
Coralline will grow if you have really good quality water, meaning zero phosphates, nitrates, ammonia (duh), nitrite etc. Magnesium is something that coralline also needs to grow, and you can test for that. Calcium is one of the main things that coralline needs to grow. If you have adequate lights, it shouldn't be a problem.
Calcium can be added by dripping kalkwasser throughout the day, also by calcium reactors, and liquid calcium. For large tanks, (180 gallons and above) I recommend getting a calcium reactor to adequately maintain high calcium levels in the water.
Have fun!