Light help to remove the green in the fish tank, pond, make it clear. Extremely efficient and This is an excellent UV-light bulb and can be used as a replacement bulb for aquarium fish tank sterilizers, germicide and air purifiers. Sometimes aquariums will encounter un-expected algae blooms and other events that may jeopardize the health and beauty of your aquarium. These events may be caused by such as, algae, and floating in your water. UV use a special fluorescent lamp that will eradicate and control these free-floating as well as disease causing pathogens when water is pumped through the unit.