Yep - the truth is that my instructor mentioned it too.
I guess it's the skeptics that get to learn the hard way?
Too bad we didn't get Dale's "feeding frenzy" on film - we could
submit it to PADI to include in their video!
Now I had worked in fish/aquarium stores a few times in my life,
so I BELIEVED my instructor when he told us that they bite...
-- I've seen trigger fish under two inches long attack a toothbrush
(just cleaning algae off the lift tube!) with as much vengence
as Jaws ever attacked a movie star....
oh! and freshwater fish too! -- there
are these little monsters called "tiger barbs"....uh huh...
...the name says it all.
When he said "they bite" - I believed him! LOL!
I keep this in mind with the occaisional crawdads we see too -- a few
weeks ago we found several HUGE crawdads....and they will run right
at you waving their little pinchers in the air - LOL! They KNOW they
can make you scream and swear if they can get you!
...on my last trip to California one of our friends picked up a BIG spiny
Kelp crab -- It LOOKED like it might work...he was holding it by the
back of his shell and though the crab wiggled and kicked a bit, he didn't
LOOK like he could reach behind him and pinch the hand holding him.
SUPRISE! 
Spiny Kelp Crabs are double-jointed, I swear it!
--- I'm not sure
I had ever heard such language come through a regulator before.
