bichirs are probably one of the safest fish to join with any arowana. I had several arowanas (Asian-when i was in my home country, Australian, Silver and Black) before and I am also much into polypterus (bichirs). I haven't had any issue.
with catfish, I haven't had any experience but some members do and from what I have been told they are doing just fine as well. Again, as advised nothing silver or shinny colored scales on the body will be one safe way to do it. (makes me think about Fei-Fung which I have seen with large arowanas-better be safe)