They'd probably get eaten by the BGK. Both species are extremely skittish at that size and act just like bait fish. They might be OK at the larger end of the size range you listed, but I wouldn't risk it with my fish.
My BGK does not bother my Archers and I had a school of sword tails in there last year for a few months that even had babies and she would not mess with any other fishes. All she eats is Earthworms.
I heard that black knife are darn aggressive, especially with small edible fish. The monster will definately stress out the armatus. Anyways, the armatus will outgrow the ATFs too so that would be risky.