Your Tiger Catfish has the potential to grow to 4', so I hope your aquarium is huge.
Dividing your aquarium is probably not a good idea, unless it's seriously monstrous, like 1,000 gallons. You'll just be cutting down on the space each fish has.
In general, Plexiglas, drilled with many holes is a good option, as it is inexpensive, safe, and with the holes, allows circulation.
Because your Tiger will grow so large, it should be fine with aggressive fish, providing you have the room, and that your Tiger is always larger than the new baby.