Yours is a spotted raphael, Agamyxis pectinifrons. Mine are striped raphaels, Platydoras armatulus. Yours should never grow beyond 5". Mine could stay around 6", but some Platydoras can reach 8 or 9 (which would not be ideal, so I hope they don't). They're all Doradid catfishes, which is a large family, but those are the ones most commonly seen in the aquarium trade.
The first raphael I got trained herself to come out at feeding time. Couldn't tell you why, other than that they are smart, opportunistic feeders, and OH and I aren't that scary. When I got the second about one a year later, she started off being very shy and hid a lot, but within a week, learned to show her face at feeding time as well, or she wasn't getting anything. When you read about them on forums, it's apparent that lots of people never see theirs and that's normal. Mine are bold. You're meant to feed them after tank lights go out, but I stopped doing that because they were getting far too fat -- they were effectively getting two feeds per day. Now I keep them on a diet by making them compete with the corys.
If yours isn't brazenly swimming out of its cave when you feed the other fish, make sure you give it some sinking catfish pellets (or even better, live worms) at night. They are very active at night and will prowl up and down the tank, probably stressing the hell out of fish who are traumatized by their predatory behaviour. If you sneak into the room at night, maybe with a headtorch on its red light setting, you'll hopefully see it.
