I wouldn't really worry about it, they're shy by nature but they'll move when they feel the need. It might also be that he is slowly acclimating to his surroundings. I picked up a baby (size of an oto) albino lf bn about 2 weeks ago and for the first 3 or 4 days I didn't see him at all, the next couple days he could be sited occasionally, now he's right out in the open nomming on the diatoms that wickedly took over his tank.