Pygos are shoaling fish. They should be kept in groups. I'm not say they can't be solo but a solo pygo will probably be a boring fish that sits in one spot all day. Which I'm sure there are exceptions. But normally the more you have the more natural they'll act.
this guy was n a shoal but i cought them about to kill his a-- so he ended up alone, he is doing well and his color is better, no stress from others. hes been alone about 6months now