Whichever site recommends Leproinus sp. for community fish is just wrong. They (at least the commonly available ones) are really sketchy as far as which fish they will harass and might eat tetras if they get in the mood to do so. Do not let the small mouth fool you, they CAN kill fish larger than themselves due to the fact that they're extremely fast and they can rip at their fins and eyes. And they will sometimes kill and eat smaller fish even if they do not fit in their mouth (mine took a liking to eating the guppies in his tank). I would not trust most of them with peaceful bottom dwellers.
Cigarfish (A. anostomus) might work, but must be either kept singly or in large groups to spread aggression. Two of them is definitely a no no, and even a small group will probably fight with each other. Some of them will also harass other species (their method is usually to go up to another fish, bite their fins, and then dart off before the other fish can catch them).
They are quite interesting though in that their mouth is on the top of their "snout" so they will turn upsidedown to eat algae and stuff.
Headstanders in general, at least the larger ones you're interested in are going to be iffy in your setup. They're one of those fish that might be just fine and very peaceful one day and then suddenly they decide to become aggressive. I've personally not had one that didn't like to harass catfish. Abramites hypselonotus, Leporinus y-ophorus, Leporinus striatus, and my Anostomus ternetzi all picked on catfish, and the only reason it generally wasn't a problem is the catfish were MUCH larger so they couldn't do too much damage. Still, as juveniles, my small y-ophorus and ternetzi ganged up on a columbian shark more than twice their size and killed it.
Also might add that headstanders, especially Leporinus or Abramites will destroy plants. My Leporinus and Abramites together (both 5 or so inches at the time) destroyed a 24" jungle val within several hours (and ate most of it for that matter - they were extremely fat afterward). So while you think your tank is heavily planted enough to sustain one of them, your plants will look BAD from getting torn up constantly.
Uarus WILL eventually start eating the neons.
I think the best bet in your setup would be to go with some type of gourami (group of pearls or some blue gourami, or something like that).
Um, that Flagtail fish "Fei Feng"
Similar to headstanders, they might destroy plants, and a large one could consume tetras.
