UV Sterilizes and Ozone
Why and Why Not

UV sterilizers have been around a long time.  Unfortunately their application has a serious flaw.  When it comes to killing the infamous Ick parasite they are close to worthless.   The parasite has 3 stages, lying on the bottom, attached to the fish and free  swimming. (See Disease Chart for details)  Now consider the the size of the aquarium and the probability that ALL the parasites will go through the sterilizer before they attach to a fish and start another life cycle – it’s mathematically impossible.  It’s better to buy healthy fish, use freshwater dips before introduction, quarantine tanks, Marine Max and / or feed garlic with food.   An ounce of prevention is worth a pound of cure.  FYI  The free swimming Ick parasites are 300 microns, filter bags or felt of 100 or 50 microns will catch them.

Ultraviolet light is just past visible light in what as known as the electromagnetic spectrum.

Ozone –  Old technology

This is one aspect of aquarium technology that I recommend you DO NOT — USE. It is dangerous for you and your aquarium inhabitants.