Had an extremely tiny senegal I got from Petsmart (was discounted due to size) that I put in a community tank with black khulis; apparently, the bichir had thought a khuli was food and ended up choking to death on one in the middle of the night. The khuli was longer than the bichir; and I still have no clue how the bichir even managed to catch a khuli in the first place. Either way, I'd definitely never recommend keeping small loaches with bichirs, regardless of size.
Also kept dojo loaches with a medium-ish senegal, and ended up with loaches with tails practically torn off and bite marks on some of their heads. The same senegal even managed to tear off most of an EBA's dorsal fin and (presumably) left a massive bite mark in the same EBA's tail; I ended up giving the EBA back to the LFS. I seem to have the most problems with bichirs cannibalizing tankmates when new fish are introduced to a tank that already has a bichir in it; most upper jaw species that I've kept chase around the new fish for a bit to test whether it's food or not.