Okay, so I have reasearching for going into a saltwater reef tank for a while now, and have looked into practically everything about a Saltwater tank. However when it comes to Refuges I feel very small and ineducated. I know they are some kind of system on the back of a tank to grow things (But even that knowledge may be incorrect) and I would like to know if I really need one for a 3ft long, 24" deep Saltwater tank. Also could someone simplify the purpose of one, thankyou. Oh, and finally, what sort of price am I looking at here?