Some people say UVs are very helpful and some think it doesn't help much. Everyone has their opinion/experiences about this. IMO they aren't necessary unless you have a massive tank (like 100s of gallons). Yes, it is extra security, but whats the probability that all the water will pass through it before the pest can repopulate, etc. It can't get rid of ick if the ick is attached to the fish, or there are pests living on the rock/sand. It's whatever is malevolent in the water and passes through the UV sterilizer. If you want, I recommend getting a phosban reactor (or some type of GFO reactor) and carbon reactor (more efficiency than a bag). They aren't necessary, but they help