i need ideas on what filtration i should have on my 75 gal saltwater tank with coral was thinking about a fluval 405 any recomendations on a budget and an ro/di unit i was looking at on ebay was a portable unit for 60$ ARE THEY ANY GOOD OR SHOULD I JUST SPEND THE 100$ ON A SIX STAGE UNIT AND FINALY I WANNA REFUGIUM AND AM NOT SURE HOW TO SET UP THE WATER FLOW IN AND OUT.