hi kathy
like fencer said dont dose for anything that your unsure of, read up on alkalinity but in order to dose one you need to know where all three stand...mag/alk/cal and what each uses daily in your system......dosing blindly without testing for the others is asking for trouble
at this stage in your tank a good quality salt will go along way compared to dosing, get your parameters at the levels you want using water changes for now and do constant testing i bet they dont change much untill your tank becomes mature and loaded with corals.
its def a good idea to practise testing for all this though even if your not dosing now that ways it will help you understand what your tank needs and usue on a regular day basis
cheers and the tanks looking great did you get your sump fixed up??