When I first got my male from PetCo (my female was always super friendly) he was a nut ball of shyness! Within a day he started swimming in the open more.
He's terrified of everything! His food (I feed live) and my finger. It's not my face either, just my finger.
I'm thinking he's scared of my finger and my female isn't because males are looked at more. And what's worse is he was there for like a month. (Maybe more!) So I know plenty of kids were shaking his cup around, poking at him, hitting the glass, etc. Therefore I think he's just scared because he thinks I'm going to do what they
all did to him. He's slowly warming up though!!
I think just give it time and put the tip of your finger in when you feed him so he'll think it's a lot less scary! Try not to tap the glass at all (even though it's tempting when they "play dead"!) so he doesn't think your finger is all that scary anymore.
Trust me, he'll get used to you!!