uv sterilizer

I see a lot of new members ask about UV sterilizers, usually right after dealing with green water or an ich outbreak, so I figured I'd put together a straightforward explanation for anyone starting out. There's a lot of half-right info floating around about these, so here's the honest version...

I have been reading more about UV sterilizers for freshwater aquariums and I am curious how useful they actually are in a normal home setup. From what I understand, UV only affects organisms that actually pass through the unit and receive enough UV exposure. That means it can help with things...