Several large Arapaimas (aka Pirarucu) are housed in a deep moat surrounding a primate island exhibit. Only this sign and common sense stops visitors from losing a finger or two.
The token feeding is quite an experience. It involves dead fish dangled just above the water, and the arapaimas would grab/gulp the fish with explosive force (and a splash)! It happens so quickly that it is almost impossible to photograph.
Check out the youtube video (not mine):
http://www.youtube.com/watch?v=yI9RGiibt7M