If your tank has always been cloudy, then it's probably dust or debris that was added in the start up. Clouds, smoke, haze (where you can see the cloud, but not the individual particles) consists of particles much smaller than 40 microns. Probably in the 1-5 micron size. That will need a lot of mechanical filtration with some low micron materials to clear quickly, although over a long time, it will gradually clear.
OTOH, if the tank was sparkling clear at one point and then became cloudy AND you had just added any physical objects to the tank (like sand, gravel, decorations), then it's more likely a biological condition (algae or bacteria.) A UV will work, but if it's a bloom, reducing feeding for a week or two will likely work as well.
OTOH, if the tank was sparkling clear at one point and then became cloudy AND you had just added any physical objects to the tank (like sand, gravel, decorations), then it's more likely a biological condition (algae or bacteria.) A UV will work, but if it's a bloom, reducing feeding for a week or two will likely work as well.
