just a word of warning, lungfish has such powerful jaw that many times the first bite is also the last bite for the victim, i.e. fatal. So there's usually no time for you to react and correct the situation. and sometimes the lungfish coulda been living fine with the other fish for well over a year before deciding to strike out of the blue.
anyway, it'll depend somewhat on the temperament of the fish, but just remember the real risk of keeping anything with an african lungfish. i personally wouldn't keep anything i mind losing with an african lungfish (or even with a SA lungfish...i had one that had bit my other fish).