One day your aquarium may look great, but the very next day it may look cloudy or have a tint to the water. This usually means some sort of algae bloom is occurring or one of your corals or invertebrates are spawning. This isn’t anything to be alarmed about, but the water will need to be changed as soon as possible, especially if the cloudiness is due to your animals spawning. Do as large a water change as possible to remove whatever is clouding up your tank, and make sure to pay special attention to your livestock. If the fish and corals are showing no signs of stress, then you have more time available to make up the water and do things the proper way. If your livestock is suffering, you may have to remove them from the system if new saltwater isn’t available to do a water change.