GUPPY EMERGENCY! MY Guppy is on the bottom of the tank and he can't move! Pleas help!?

He looks like he is dead, he is just sitting there. I know he isn't because one of his fins are moving. I tapped on the tank and he didn't move (It looked like he was trying though.) I pushed the pebbles away to make sure he wasn't stuck and he just floated to another spot! Is there anything I can do to save him? My other fish seem fine!