I have kept this species (Hyphessobrycon megalopterus) several times, though not presently. They do remain in the lower half of the aquarium, always; they will come to the surface to feed, though they prefer waiting for the food to sink and drift past them. Of the several Rosy clade species I have kept, all are the same in this respect. They also do not like light. Mine remain under cover of plants, and on the right half of the tank out of the direct water current.
You definitely want a mix of male/female. Half and half works fine, or even more males. The males in this species, and in the other Rosy clade species i have kept, do not drive the females like some characins will. Watching the males displaying in pairs is fascinating. All species that I am familiar with in this clade do this. Two of my Roberti tetra males were into this last evening, fins spread, almost black in colour, gliding around the tank about an inch apart, circling and charging, quite impressive.
Last edited by Byron; 08-27-2011 at 02:24 PM..