Ok thanks for the tip on the Arowana but the issue with the common bichir tankmates is that my petstores generally keep small ones which are nice little snacks.I'd say no on the arowana unless you are planning on upgrading rather quickly.......I believe the consensus is 150g for a single arowana. I'd do the Ctenpoma(sp) also known as spotted african leaf fish. Also tiger barbs 'bout 7-9 (odd number) would go well as well. They are playful and will nip at each other in that bunch leaving your bichirs be.
My .02
