Yes these are some of my favourite fish.
I've owned acestros, ATFs, and several species of vampire tetra, and the cudas were the most fun by far.
They're lightning fast, they'll nail anything alive and small enough to eat as soon as it hits the surface, and their accuracy is amazing.
They also do a superspeed U-turn when they nail a feeder.
They don't grow too big, falcatus/altus are probably gonna end up 10/12 inches in an aquarium, but they need a lot of room.
When mine were 6 inches or so, I tried keeping them temporarily in a 12 inch wide aquarium, this was way too small for them, they were nervous and very skittish.
As soon as I moved them into a 150 they changed completely. They need a tank 24 inches wide at least. They were happy and active and hungry and calm.
You should have lots of free swimming space as they are midwater, and very very fast. Don't put lots of wood in. A few plants are fine.
Don't mix them with cichlids or anything that would pick on them, bully, want to fight etc. So no cichlids, no dats, no aggressive catfish etc.
They are pure uber predators, not fighters/brawlers, they would just get picked on and not have the instinct to fight back against cichlids etc.
They go fine with bichirs and peaceful catfish and maybe some barbs etc.