They will be fine as long as the peacock is big enough for the bichir to not be able to eat it and they have enough hiding spots. Spiney eel have small mouths but bichirs can be a bit bitey towarrds small wormlike fish. You didn't mention what bichir species so I'll say stay clear of any species except senegals, palmas or possibly delhezi. All the others get too large to be kept with a peacock eel for very long, although if you do get something like an ornate make sure you can seperate them before the size difference is too great, I have seen pictures of bichirs that have died while trying to eat a not much smaller bichir, this results in both fish perishing so be careful . Also make sure you have a good fitting lid for the eel.
I have grown a 5 inch fire eel up with 2 9inch senegal bichirs and there has never been any issues or fighting at all.
