Read and when you are done reading read some more. It all depends on what you want corals? Fish? Budget? What are you looking to do with this tank? You for sure need saltwater, live rock or base rock, sand live or not, salinity instrument refractometer or hydrometer, testing kit, cycle the tank 4-6 weeks usually, upgraded lights if doing coral. Initial startup saltwater needs to be made from rodi water and daily top offs of rodi could be routine. Biweekly or even weekly water changes.....just my two cents really need more info from you