Sorry to hear that, I had 2 knifefish when i first had my 120gallon 1 knife loved the hideing spots and the massive tank ( they were 1 ") the outher 1 hid behind my protein skimmer.
sory to confuse you guys but i found out he wasnt dead right after my last post but i had to leave. so he still seems fine and is hiding in a cave now and is verry much alive. im happy and sorry for the confusion this thread causes.
well he was laying on his side and i didnt see any gill movement. but i think i just didnt see him that great because he was in a spot that is hard to see.