You wouldn't guess they have teeth, but believe me, they do. They've got a wicked bite as well... I've been bitten by mine, and it's not pleasant. Bite's alot worse than any other bonytongue I've experienced (jardini, clown knife, asian knife). I'd compare the bite to something more along the lines of a similar sized snakehead or aba aba. These knives aren't as thin either, they're a bit thicker and more heavy-set than their relatives. When it was smaller, around 5-6 inches when I first bought it, it ripped the entire caudal peduncle off a 4 inch sleeper gudgeon. The managuensis was a decent sized male (~12", give or take an inch or 2), and was no pushover. The knife got him at nighttime though, he more/less stayed out of the jag's way during the day. At first the managuensis had a few ripped fins, and a few bite marks on the body, but being in a community of aggressive cichlids, I didn't really think anything of it. Then one night I came home late and I heard splashing downstairs. Turned on the light, and I saw my cichlids all flying around the tank, with the knifefish just nipping randomly at anything that it came across. The managuensis would run, turn around and flare at the knife, which would back down and swim around a bit and attack it from behind. The jag was ripped up pretty badly by the time I got home, and a few days later he died in a quarantine tank from a fungal infection 
During daytime, the knife only came out to eat, or to chase away another fish that came too close to the entrance to his cave, other than that he remained hidden with just his head poking out. They're almost constantly watching everything going on in the tank, they're rather cautious. Others on this board have had them kill off plecos and such. I eventually sold it because there was so little I could keep it with (asian RTC that it wouldn't mess with, and a few bichirs).
Here's a decent picture of the mouth structure, it's alot more heavy-set than most other knives:
Refer to this thread for another member's experience:
http://www.monsterfishkeepers.com/forums/showthread.php?t=127480
During daytime, the knife only came out to eat, or to chase away another fish that came too close to the entrance to his cave, other than that he remained hidden with just his head poking out. They're almost constantly watching everything going on in the tank, they're rather cautious. Others on this board have had them kill off plecos and such. I eventually sold it because there was so little I could keep it with (asian RTC that it wouldn't mess with, and a few bichirs).
Here's a decent picture of the mouth structure, it's alot more heavy-set than most other knives:
Refer to this thread for another member's experience:
http://www.monsterfishkeepers.com/forums/showthread.php?t=127480
