DO this. At your lfs or online from one of our nice sponsors, get:
1. Salifert alkalinity test, magnesium test, calcium test.
2. Kent DKH Alkalinity Buffer, Kent Tech-M magnesium supplement; Kent Turbo calcium.
I name these in the interests of telling you something easy to find that I know is easy to read and use. They match each other. If alk is low, dose buffer by instructions, wait at least 12 hours, test again. Mark your parameters match mine.
Be sure your lights are at least T5 reef lighting.
Start a new coral on the bottom. Superglue it to a piece of limestone rubble (your lfs will have this for sale) and move it up gradually until it looks happy and spreads out.
Run tests every week and write down the results in a little book you keep.
If something starts to drop, like alk, eg, dose a little to correct it, and re-test in 12 hours and see if it fixed it. If everything is screwy, dose mg first, until it's right, then dose alk until it's right, then dose calcium until it's right. I don't know what they sold you, but take it back and get the test kits. They'll last you at least a year.
Also get some nitrile exam gloves (pharmacy) to use when messing with corals. You and they will both be happier.
There's a little post over in Reef Discussion in the stickies called Dirt-simple Chemistry---read that. It'll explain more.