dprush83 what species of polypertus is your bichir? As there is not alot of information on them it might help to narrow down the search
Polypterus ansorgii :common name,Guinean bichir
Polypterus (bichir) bichir: common name, Nile bichir
Polypterus (bichir) katangae
Polypterus (bichir) lapradei
Polypterus delhezi: common name Armoured bichir, banded bichir
Polypterus endlicheri congicus: common name, Congo bichir
Polypterus endlicheri endlicheri: common name, Saddled bichir, Red bichir
Polypterus mokelembembe
Polypterus ornatipinnis: common name, Ornate bichir
Polypterus palmas buettikoferi: common name, Buettikofer's bichir
Polypterus palmas palmas: common name, Marbled bichir, Shortfin bichir, dinosaur eel
Polypterus palmas polli: common name,Poll's bichir
Polypterus retropinnis
Polypterus senegalus meridionalis
Polypterus senegalus senegalus: common name, Senegal bichir, Grey/Gray bichir, Dinosaur eel
Polypterus teugelsi
Polypterus weeksii: common name, Weeks' bichir, Fat-headed bichir, Mottled bichir
All sounds fine in your tank and I am not surprised to hear of the color change as some do become darker or lose their bands as they mature.
How long have you had your bichir?