I think the Needlefish is the odd-man out, sorry needlefish, take a hike.
But maybe I'm to quick, what particular type of Needlefish is this? There are over fifty types listed and I'm sure only a few are readily accessible to aquarist. And aren't most needlefish generally brackish to salt?
You might, might, could get away with the Oscar and the Clown Knife being as they are compatible in general (have to see what your Oscar decides when he matures). Both the O and CK in a 80 is a tight fit, the CK can get up to 36" = 3'ft! They'd be better in a 125-150gal.
But lets be realistic, somebody is going to have to go and the Needlefish is the least compatible.
Your O is acting like a O... He's pouting about the change in his enviroment.
O's are very funny that way, they pout, throw temper tantrums, refuse to eat and display all manners of good and bad personality traits.
Some are very mild mannered, some won't tolerate any other fish....