I agree that the fish needs a bigger home, 55gal at least, but as long as you are trying to improve his home, that's good. I would start saving some $ for a Craigslist 55 or larger and maybe a new friend, after it's quarantined! Since he has lived alone for so long, a good, long QT would be a very smart idea.
Actually, if you watch CL for awhile, you will find free 55s and items, so that is even better!
How big is he anyway?