The best filtration for a reef tank is live rock...about 1.5 lbs per gallon along with a sandbed of about 3-4". This along with a protein skimmer will help maintain the high water quality needed to keep corals and anemones. The LR
and sand presents a large surface area for nitrifying bacteria to grow on and carry out biofiltration. The deep sand bed can provide a low oxygen enviroment for denitrifying bacteria to grow in helping to remove nitrates.
A reef tank can be more demanding than a FO
tank. Water quality must be more closely monitored and some corals and most all anemones require intense lighting, water flow and special feeding. Do a lot of research before jumping into the reefkeeping hobby. It can be time consuming and expensive but is definitely worth every minute and penny spent. HTH