I was hoping for that too. I was also hoping for the jau and piraiba to effect a difference but lost both cats on transfer. The ISN was always selective in choosing his dislikes and it looks like when it does, the size of tank doesn't matter.
And yet if you netted another identical small fish out of another tank and dropped it in here...I doubt it would last 60 seconds.
I think that once a small fish manages to survive for more than a few days in a dangerous environment like this...especially a smart fish like a cichlid... it learns all the escape hatches and hidey-holes, and loses that "panic vibe" that was displayed when it first was introduced. That in turn projects a more relaxed, non-predator-exciting behaviour and the big guys don't get all caught up in chasing and eating it because it isn't frantically running away with "EAT ME!" projecting out of it.