UV Sterilizer?

[taichimaster]

I've been reefkeeping for one year now. I have been reading about UV Sterilizers. My water is really clean and I use carbon. I was wondering if a sterilizer is necessary. Please give me your thoughts.

 

[SeaMonster]

I believe its used to kill parasites. recommended that you turn it on for a few days after buying a new fish. I've also read that they are not recommended for reef tanks as they kill the good bacteria as well as the bad.