Once I had three small clown loaches in a 55 gallon tank, and I knew that I was going to need to rehome them relatively soon.
Then, one day I saw this pathetic clown loach at the lfs. His former owner had dropped him off because he'd gotten too big. He was about 6 inches, stuck in a tank with a bunch of catfish. He had no hiding spots. The only object in the tank was a flat piece of driftwood, and the loach had scratched his head up trying to wedge himself underneath it.
He was only 12 bucks. At first I didn't buy him, because I knew I already had clown loaches that I couldn't take care of in the long term. But I couldn't get that poor guy off my mind, so I went back in a couple of days and bought him. He was in quarantine for a few weeks. It was so much fun to finally put him in the 55 and let him meet the other three little guys.
I kept them all for about another 6 months, and then found them a good home (with Zebulon who's here on AC). They live with Zeb's old loaches, plus a group of little babies he got recently. He's got them hand-feeding

My rescue fish is the largest one in there, so he's the alpha loach.
So, in my case, I'm totally happy about my sympathy purchase. That fish went from being miserable, lonely, and scratched up, to fat and happy and king of his tank.