Upon adding Clarity™ to the water, you will see a cloudy haze begin to form. This is normal and means that Clarity™ is beginning to work. The water is filled with tiny pieces of floating matter that were not visible to the naked eye. Clarity™ makes those pieces of matter begin to clump together. As they clump together they form larger pieces of matter that are now visible, hence the cloudiness. Once this matter has clumped together, it is a simple matter of mechanical filtration to remove the residue. Matter that was once too small to get caught in filter media is now in large enough clumps.
In order for Clarity™ to work effectively, you should have a filter with mechanical filtration (e.g., filter floss) connected to your aquarium.