What is a sterilizer used for?
 

And don't say to sterilize!!

I suspect you are referring to a ultraviolet sterilizer. Mainly It's used to kill algae and pests some that live in the water.

to sterilize of course :)


Ok, ok... like ezy said, the main things they do are remove parasites and algae. They're not all that effective though, IMO, because they only kill what passes through them.