Can you guys give me some small predatory/carnivorous fish recommendations?

[Fanatic_Fish_Lunatic]

A bit larger than 6 inches, but red wolf fish is a good option for that size tank. Perfect mini predator with a great feeding response. As long as you don’t have any holes for it to jump they are very hardy fish that will eat anything.
I’d hesitate to do exodons in that small of a tank. To do a large enough tank I wouldn’t do it in less than a 4 foot system.
Since you’re in SE Asia, have you thought of smaller snakeheads?

If I can help you get the idea, I want something more similar to killifish, African leaf fish or badis. Something like that.