Ive had to place my 8" silver with my Moba colony temporarily due to aggression with no problems. It was in there for almost 1 month and eating well.The arowana made good use of the upper portion of the tank, as the Fronts usually stayed low-mid regions.
Besides the obvious differences in parameter requirements for the two, I wouldnt recommend this as some Fronts are brutal/territorial and could easily kill the arowana.
Cheers=)