For Bichir companions i recomend:
-Spiny eels
-synodontis cats
-other bichirs(obviously)
-knifefish
-purple spotted gudgeon
-ropefish
You have not said what kind of bichirs they were, there are lots of different species ranging in size from 25cm to 1m. THe most common are the ornate bichir (polypterus ornatipinnis max size 60cm in the wild), the senegal bichir (polypterus senegalus max size 50cm in the wild), polypterus palmas palmas (max size 30-40cm in the wild [i think]) and the saddled bichir (polypterus delhezi max size 45cm in the wild).
I would recommend the senegal and ornate they are the easiest and the most common (but the ornate can be very expensive sometimes, i have seen adults on sale for £60)