Don't listen to people that say you have to keep Jarinis alone. Look at my videos in my signature to be proved otherwise.
In my experience, Jardinis are more agressive to fish that share water space with them. This means middle to top dwelling fish. Bottom dwellers are almost a for sure tankmate as long as you have some places for them to hide. Usually if they break line of site with the arowana he'll leave them be.
I had a P. endlicheri endlicheri with my jardini for almost a year before he had an "accident". My jardini never so much as looked at him, even when he swam to the surface to gulp air.
I also keep a common pleco, small rafael spotted catfish, fire eel and 8 clown loaches with my 15 inch Jardini. They're all I've found that he won't try to establish dominace with.
Keep in mind though that Arowanas are pretty intelligent, relative to most fish, and because of this they all have their own "personalities". Just like people, sometimes fish can just be jerks. It's really a fish to fish case, just test out what you'd like to keep with him, if there's a problem just be ready to remove the new tankmate and you should be ok. Eventually you'll find something that works with your Jardini.
In my opinion at least, I'm sure some will disagree with me. Mostly due to my above point, each fish is different. Just because their Jardinis kill everything doesn't mean your's will.
Nutshell: As long as their size is similar your bichir should be alright. You could also have just as much problems with the bichir biting at the Jardini's fins. Play it by ear and let us know how it goes. =D