On the question of light ... is it where you put it, or did it go for a walk to find this spot? If the nem chose it then I wouldn't be worried about too much light. Somewhere I read that lighter colored ones need more light, darker colored ones need less. Only two have moved around on me. A light colored one moved 4" to get less shade but stayed near the bottom of the tank (supposedly should have climbed). A dark one was near the bottom of the tank and kept climbing until it is just 1/3 down from the water surface (supposedly should have liked the deeper area better). I just figure that now they will sort themselves out after I make a suggestion of where to live.
You could try putting something on your tank lid to cast a bit of shadow on it and see if it gets happier. Like a postit note or something else that's sorta translucent. But if that is the issue he should migrate on his own (unless it is already at the bottom of the tank). The only downside of these things is how hard they are to move when their foot is deep in a rock crevice.
