What is the best living filter?

[Scavenger]

I've heard of all sorts of life filters in the sump or fuge,but have no first hand experience:

1:Live Oysters. (if one dies your in trouble)
2:Mangroves
3:Aipstatia farm
4:Xenia
5:Button Polyps

There is an interesting video on sump design here with live filters incorporated www.reefvideos.com (2nd vid from left on top row.)

Hope some of this helps.