wolfgang is right depends on size of tank , for larger tanks i would reccomend a sump as this serves more then one purpose you can hide all your equipment ie heater skimmer ,
leaving only power heads in tank
you can have different sections in sump (depending on size) bio filtering, refugium, natural filtering section ie miricale mud deep, sandbed, caulpera, cheato,
LIVE ROCK is a must wot ever size you going for ,as live rock is a good natural filter and contains lots of life for your aqaurium , (some not good)
if you google the above and get more detailed info on each item and understand more ,
there is to many different ways so read read read and when ya think you know enough read some more , but imho live rock and live sand is a must the rest is personal prefference so reading is a must
also a cannister filter can become a nitrate factory if your not careful