UVS=Ultraviolet Light System. It goes in line with a canister filter, or can be used with a pump. It will eliminate water borne bacteria; at higher wattages it will eliminate protizoans & parasites. It is also good for algae.
Prophylactic treatment of diseases is a bad idea; this is how drug resistant strains of bacteria are created. This means that if you need the med to work in the future it probably will not, especially in the case of antibiotics. The only time I would advise medicating a well fish is in the case of wild caught fish. This is when a worming protocol, with the proper medications would be a good idea.
Since most of your bad bacteria are water borne, the best preventive medication is fresh water. If you change 50% weekly, or 30% twice weekly in a tank stocked properly with healthy fish you will rarely have problems.