It's only been a few days so maybe soon he will start acting aggressive. Any recommendation on live food? Just feeders? I can put them in a spare tank with my crayfish as a quarantine. How many days to make sure they're healthy feeders?
If you are going to use live, I'd just go with rosie reds. They need a separate tank from the crayfish since a lot of meds are super hard on inverts. You need to treat at LEAST 1 week, but 2-3 weeks is best. I would use something along the lines of API general cure or Seachem Paraguard (which is what I treat my feeders with). Observe them, remove KIA from the tank immediately, and look for signs of anything parasitic or fungal which is 99.9% of what you'll be dealing with in this case more than likely.