UV sterilizers only kill off bacteria, algae and protozoa that pass through it, so it will not cause harm to the beneficial bacteria growing on your biological filter or your live sand and live rock.
It is important to note UV sterilizers do not kill algae attached to rock, sand or parasites attached to your fish. Many parasites do have a free-swimming, water-borne stage in its life cycle. A UV sterilizer helps reduce the population of harmful parasites by killing them off in their free-swimming stage.
Installation is very simple. The sterilizer simply hangs on the back of your aquarium and water can be supplied with either a powerhead or a canister filter.