I am not sure what this cloudiness is in my aquarium. I did an 80% water change and the water was clear for a day, and then became cloudy again. This is a relatively new tank and still have ammonia readings. An up close examination made me see that it looks like very very fine dust like particles in the water, so I donít know if itís my water (itís well water, quite hard), dirty water (waste buildup), or just bacterial bloom. When I first set up the tank with no fish, there was no cloudiness.