Einstein developed swim bladder disease, which caused him to turn upside down and sink to the bottom of his tank.
His owner, warehouse worker Leighton Naylor, was so distressed by the sight of his struggling pet, he knew he had to take matters into his own hands.
"He's always been a fighter so when he sunk to the bottom one day and couldn't get back up again it was a very sorry sight.
"It broke my heart to see him so helpless. He looked so depressed," said the 32-year-old from Blackpool.
He made Einstein a "floating frame" from recycled tubing, which fits perfectly over the fish's two-inch long body.
"I wanted to build something that would allow Einstein to move his fins a little bit and be comfortable at the same time," he said.
"He wriggled a bit a first and he wasn't too keen on the idea. He kept catching on to plants and getting stuck but since I've rearranged the tank to make it disability friendly he's been absolutely fine."
Video: http://www.telegraph.co.uk/news/newsvideo/weirdnewsvideo/10013956/Life-jacket-helps-disabled-goldfish-swim-again.html
A fish that can't swim... Now there's something I never expected to see.