I had a group of 4 that went thru the divider and got eaten by a pair of female Sagittae. Only had them like 3 days or so. They don't have very big mouths, so theres that. They are more like an armored Cory cat that's popping steroids
You need to upgrade the 50g to a 75g, and then you can get Pimelodus bufonis, bumblebee on steroids or gulper. That 50g is pretty limiting in getting a predatory catfish that is different from the other tanks.
It takes a bit of work to dilute the pollution in a 50g with an adult size gulper. They just eat so much. You're looking at least 2 fin level changes every week.