I bought a silver arowana yesterday about the same length as my bass and woke up this morning and the aro was gone and my bass had a big belly. That was a 50 dollar snack for that greedy little F***!!
Sorry for your loss. Pbass know no difference between an aro or a goldfish. Recommended that small arowana are kept without tankmates until 5-6" long. Also not to be mixed with cichlids(cichla) until the aro is 10-12" long and twice the length of the cichlid.