:( :( :(
Tailbiting is a real beast to figure out... Do you have an airstone lying around? Sometimes they like to play in the bubbles for a little bit. Maybe that will give him a bit of entertainment and distraction... I wouldn't leave it in there overnight or anything, though. Just for like 15-30 minutes. And of course, if he looks stressed out by it, then take it out.
My fish likes to swim through the bubbles and pop them, especially if some of them accumulate under his bridge.