From FrugalReef

[edit] Bacterial Bloom

White or cloudy water that is not the result of stirring up the sand or aragonite used to construct the fish tanks substrate is usually the result of what's called a bacterial bloom. It's not unusual for a new tank to go through a few of these after setup.

Bacterial blooms are almost always caused by overfeeding. The left over food becomes food for the bacteria and they propagate exponentially until they're so numerous they make the tank water cloudy. Make sure you're not feeding your fish more often than a couple times a day, and make sure you're not feeding them more than they'll eat in a minute by themselves.

Normally the bacterial bloom will resolve itself in a few days. A partial water change or two would be a good idea to reduce the bacteria and dissolved food in the water. You might want to only feed your fish every other day for a while to help as well.

[edit] Algae Bloom

Green cloudy water is an algae bloom. See Algae for algae control methods.