before you start throwing in meds. check your water parameter. Do a water change first. Fins clasping could mean a lot of things-sick, poor water, stress.
What color is his poop?
what's the water parameter?
bigger tankmate?
I had the same prob with my FH when I got him.
Sounds like he's stressed.
Just make sure your water conditions are good,and give him a few day's.
He'll come around
