I have six of these fish in my community tank - 2 males, 4 females. They are lovely little fish. I have them with small fish so I don't know how they get on with larger ones. I have them with honey gouramis, green neons, galaxy rasboras (or whatever they're called now), habrosus corys and dwarf chain loaches. The males chase the females, and 'display' to each other - there was a link to a video of 2 males doing this posted recently, but they've never chased anything else.
They eat pretty much the same as my other fish. Because all my fish are small, I crumble the flake and they eat this readily, also frozen food such as daphnia and cyclops, as well as mashed peas.
They seem to do fine in my tapwater which is pH 6.8 with medium hardness. I think they're supposed to be one of the easier pencilfish, some can be hard to acclimatise.
HTH