how long has the tank been running? a bacteria bloom can make your water cloudy. if you change too much water at once and clean your filter at the same time, it can cause a tank to go through a mini cycle and you will have a bacteria bloom. new tanks also are cloudy as the bacteria develops. this is good bacteria for the bio filter. over feeding can cloud water too. high nitrates and leaving the light on too long can cause single cell algae which also makes the water look cloudy. this has a slight green tint and you will see some green in your filter floss.