Fish tanks become cloudy when there is an abundance of new microscopic life such as bacteria, micrometazoans and protozoans, which can be churned up by moving rocks or decorations in the tank. New aquarium owners often mess with the environment too much and never let the water settle on its own, creating an ongoing cloudy aquarium problem.
The cloudiness in the aquarium usually begins when the aquarium is first set up, and will dissipate on its own after approximately a week if the tank is left alone. However, feeding fish can also introduce new microscopic life and can sometimes lead to cloudy water.
To treat the aquarium and keep cloudy water away, try putting good bacteria inside of the new tank. This can be done by taking a few scoops of gravel or a filter from a more established aquarium and moving it to the new aquarium. Changing the water routinely is also key to keeping cloudy water at bay, as is regular maintenance of the filters. Filters help to support the fish living inside of the tank, and should always be clean and functioning properly.
Another tip is to feed less food to the fish. Many new fish owners feed their fish too much, and end up leaving lots of waste in the water tcreating cloudy water.