Thank you Sakura for taking a look. You're always so kind, sweet, and knowledgeable!!!! <3
I didn't know what fin rot was supposed to look like. Thank you for the description. His fin edges are definitely not marker-black so you must be right about the pigmentation.
He finally ate this morning instead of bolting like scaredy cat. He's also zooming around like a bouncy ball on caffeine. And sometime between when I left and came back a few hours later, he managed to build a large bubble nest across the front of the tank
Should I stop fin rot treatment and get him into a more permanent home? I can continue to dose with stress coat but if he still needs aq salt, I'll keep him in the 3 gallon.
Thanks again for all your help. I'm sorry I keep posting false alarms
EDIT: Here's another pic of his tail flared out.