Does he seem to be floating towards the surface, or is he struggling to keep the "altitude" in the water? Is he acting in any way differently from usual aside from the strange position?

If he is, he probably has gotten some swim bladder disorder, but it can be treated easily with salt and shelled peas! Since there're no parasites involved, the salt solution doesn't have to be very strong, one teaspoon per 5 gallons of water should be just enough. And the peas should be natural, no salt added. Buy frozen peas, and thaw them and pop them out of their shells before you give them to your fish! If he's not quite used to sinking food (if his staple diet consists of floating flakes or pellets), no worries, he'll find them on the bottom for sure! And he'll only start noticing them better if you'll start giving them to him regularly (:

If there's nothing else strange about his behavior, I think you could just wait and see (: