I have 2 bichirs and a jardini in a 180gal tank. They have been together for a year now. We went out of town for 10 days early July and when we got back 1 bichir is missing. My jardii is approximately 18 inches (+/-) and the missing bichir is maybe 6-8 inches. Before we left I have predicted that my jar will eat the small bichir due to hunger.
As long as you feed and make sure your jar is full everyday, the tendency to eat or attack the bichir is very slim.