Haven't seen any rounded bending of a bichir's spine like that before, though the red and frayed ventral fins make me suspect a bacterial infection of sorts. The belly doesn't look full as a result of food IMO, and fluid buildup/swelling seems more likely. I doubt that it crashed into a wall at breakneck speeds, but I suppose it's not out of the question; I don't know if the spine would've gradually curved towards the midsection of the fish if it did indeed hurl itself at a wall, however. Perhaps
Hao
or
giseok jung
could help?