I'd be worried about the armatus than the bass....Armatus are big pussies, bass on the other hand are very aggresive when it comes to feeding. A school of bass are the worst eater..
You may be able to get away with 1 armatus and 1 bass..it depends on the temperament of the bass. Forget scombs or tats...they're even bigger pussies.
Armatus ae best kept with either bichirs, rays or gars...
stan