I received a bag of 1" juvie ornatum/gephyrum back in Feb 2013.
Did some research on the rivers they come from and found low to mid 70sF are average temps.

Put them in a 55 gal to grow out, where they almost immediately were very aggressive with each other. Added some 1" tetras as dithers, aggression continued.

Afraid the aggression would become lethal, I added half dozen 2" Guianacara, and the aggression subsided.
They grew slowly but steadily, and the largest hit about 7" at the end of 2014.

I find them to be very susceptible to bacterial infections if water is not pristine.
The moment I let nitrate rise to or above 10ppm, by neglecting my "minimum" twice weekly water changes, I would notice a deterioration in health.
I never found them to be overly aggressive with any other species, and kept them with the Guianacara the entire time, moving both species to a 150 gal tank once they hit about 3".
