cardinal rule of dosing chemicals is not to dose anything you can't also test for.
in your shoes, my first move would be to get a set of good tests and check levels of nitrate, phosphate, calcium, and alkalinity. post your results when you get them and folks will be able to help you with any adjustments you might need to make.
Well,first things first.
You need test kits for Calcium,alkaline and Magnesium.
Then I would say those are the big 3 to be concerned about.
What type of corals are you planning on,stoney(SPS),leathers,softies?Lighting os also pretty important,depending on what corals you decide on.
you wont need chemicals at the moment, and as mentioned by the guys you need to test params first, otherwise how will you know if you need to dose, i personally dose kalk and baking soda, but i test my params