Cloudiness is usually caused by a bacterial bloom, which are usually harmless. Cloudiness is common in new aquariums.
If your water is cloudy, then you should:
✔ Increase the aeration and make sure that the filter is working correctly.
✔ Siphon the gravel and change a small amount of the water (15-20%) regularly until it goes away. Remember to add a
de-chlorinator to the tap water.
✔ Test the water to make sure there is not an underlying problem.
✔ Sometimes cloudiness can be caused by over feeding, or by failing to remove uneaten food. If this is the case, then
you may have a water quality problem