Aesop;1502781; said:You should be ok. The eel has an EXTREMELY small mouth and I highly doubt the arowana can fit in it. I have a fire eel with my jardini arowana, although they are bigger the arowana is like 15 inches now and the eel's probably about 13 or so. They get along well however.
The eels are pretty smart, and seem to know to stay out of the way of more agressive fish.