They won't take out your bacteria like everybody thinks they do.
They STERILIZE, that is why they are called a UV sterilizer. They don't kill anything, they keep it from reproducing.
Do yourself a favor and run one, this is not a cheap hobby, do it right or don't do it at all.
However you may want to consider running ozone. It is cheaper to maintain, you don't have to buy 40dollar bulbs every year, and you don't have to clean it.