First thing is to look for any visible signs of distress, such as white spots or cloudiness to his skin, which could indicate ich, marine velvet, or a problem with the slime coat. Also, watch for behavioral issues such as clamped fins, excessive rubbing on hard surfaces (not to be confused with normal clownfish snuggling behavior). Is he plump, or thin?
Odds are, he is simply stressed from the move and will perk up, especially if he is eating well and actively chasing food.
On that note, what are you feeding? A varied diet is always best.
Also, assuming you only have one, if it isn't female yet, it likely will be soon.
Someone stop me! Please! But... not just yet...
55 Gal Tropical FW
55 Gal Mixed Reef