Edited thread title to something relevant and moved to Other Characins
Red tail cudas need fairly specialized care. They're exceptionally difficult to get off of live, they spook very easily, and they're very timid feeders compared to things like cichlids or most catfish.
If you're wanting to keep redtail cudas, provide them with a calm tank with enough decor to both keep them from getting spooked and to prevent them from building up too much speed, and avoid any tankmates that would outcompete them (which is basically everything lol)
It CAN be done, but it requires a focused effort on the cudas to allow it to happen. If you just drop a few into a typical MFK style community, the odds are heavily against you.