i can tell u there very very very painful..they almost make you not able to move only so your skin has no movement so the pain will not increase....
http://www.monsterfishkeepers.com/forums/showthread.php?p=3353019&posted=1#post3353019
http://www.monsterfishkeepers.com/forums/showthread.php?p=3353019&posted=1#post3353019