Gary you can try this with the koi in your pond
The owner of a fancy goldfish with buoyancy problems has designed a special sling to help it move around.
The video below was posted onto YouTube and shows the goldfish swimming around in the aquarium with her tank mates.

The fish's owner 'synirr' says: "She has trouble maintaining buoyancy on her own. She looks a little silly, but it is better than lying at the bottom of the tank all day!"
http://youtu.be/qsRwn20xAco