Help with Goldfish swimming wierd!

aurora

Small Fish
Oct 17, 2005
12
0
0
Scotland (Glasgow).
#1
Help ?

:confused:
Hi everyone. First time here. I have a tank with 3 fancy (comets,I think) goldfish. The tank is 48 inches /18 inches/12 inches. The fish are all around 10 years old. One of them has recently started acting weird. He is the biggest one, at eight or nine inches long and to see him in the state he's in is quite distressing. He seems unable to keep himself upright, turning over and over (like a dolphin doing tricks). Then, next thing he will be off, tries very hard to swim around normally, but after maybe 10 seconds or so he's back to spinning around and floating up towards the surface. When he gets there, he darts back down, only for the whole process to start over. Please help. I don't know if he's dying, and would rather save him the agony and try some humane way of letting him die quicker. He tries to feed when I put food in, but after managing a couple of flakes he stops.
All advise welcome.
Thanks so much.