All UVCs (ultra violet clarifiers) make use of the same principal: using ultra violet light to kill germs and where pond hobbyists are concerned to get rid of green water which is the result of a bloom of the one celled algae.
Algae is a plant and when there is sufficient sunlight, food, and carbon dioxide they bloom resulting in the pond water turning green. It can be so dense that you cannot even see your fish.
This is where the UVC can help.
UVC can disintegrate the one celled algae which is so small that it passes through most filter materials. Like pouring coffee through a sock and it still comes out black.
Whether it is a cheap or a very expensive UVC, you will find an ultra violet bulb inside. The bulb will be encased in a waterproof glass container. Surrounding the glass container will be a casing with and inlet and an outlet attachment through which pumped water will flow in and out.
The green water containing the algae will pass over the glass tube and the bulb will kill the algae by bombarding it with ultra violet light. The dead algae will clump together and becomes big enough to be trapped by the filter material. And as more of the algae are removed, the water gets clearer. Resulting in clear water.
While the pond water may be now clear it does not mean you have good water. Because toxins like ammonia and nitrite may be present inside. To get rid of the toxins a proper biological filter is necessary.
