It looks like there might be a couple things wrong.
1: In the photo, I don't see any hiding spots for him. Like the person above me said, JDs love a good cave or two. You don't even have to buy a new one. Just take some of that cool looking rock you have there and pile it up (make sure its nice and stable) into a little cave.
2: This may seem trivial, but I see it a lot and it seriously stresses the fish out. The bright pink sand is a big no - it tends to reflect a lot of light back into the fishes' eyes, and stresses them out (to fish especially fw fish, bright colors usually mean stay away - plus, its unnatural and could make them feel like they aren't in their natural habitat.) My dempsey loves the white marine type sand I bought for him/her. They sometimes sift through it like geos.
3: Your water has that "new tank" look to it - not cloudy, but it has a blueish milky sheen to it that I only see in new or just cleaned tanks.
All in all, your tank looks well oxygenated, but it's too open for a cave loving fish. You can also try live or frozen bloodworms - mine adores them - or even brine shrimp, live is best. Guppy fry work too. If he takes them, start to feed dry or dead food with the live or frozen food to entice him to wean off. Good luck! He's adorable, and I hope you get him to start eating.
