When aquarium water is cloudy, it means that there is a lot of microscopic life inside of the aquarium, such as protozoans, bacteria and micrometazoans. The cloudy water is ideal for newborn fish because they feast on the microscopic life; however, it is not necessarily good for adult fish.
Cloudy water also makes it difficult to see fish and can turn an aquarium into a nonvisible display. To avoid cloudy water and to get rid of existing cloudy water, it is recommended to allow time for the water to settle down while also ensuring that good bacteria is added to the tank. Prepackaged bacterial cultures can be added or adding in a few live plants can also do the trick. Setting up a filter and water change schedule will also help keep cloudy water at bay.