So what do sponges actually do?

[Damsel13]

I have alot of sponges but I was wondering how they help my reef. Anyone want to fill me in?
Thanks for reading this.

 

[drummereef]

Dr. Shimek can explain it much better than I.

http://www.reefkeeping.com/issues/2005-06/rs/index.php


And a good Podcast.
http://www.advancedaquarist.com/2006/10/podcast