What kind of corals have you added to the tank? Exactly how long has your tank been set up? If it's only been up a couple days and you ahve live corals in the tank, I would recommend that you bring them back tothe LFS. Your tank needs to cycle before you can start adding delicate creatures in the tank.
Could you please provide us with more information on the tank and set up? What kind of lighting do you have? What size tank do you have? How long have you had the water in the tank?
What are your water parameters at the moment? Amonia, Nitrite, Nitrate, Calcium, pH, Alk, temperature?
Also a milky white appearance in the water could be caused by a bacterial bloom due to high levels of ammonia in the tank.
The more information you can provide the better off we'll be able to help you and your animals out.