Question about our fancy tail goldfish...?

He could have gulped too much air, or he may have an infection in his innards. Do you feed him flake food? When feeding, do you sprinkle the food in, or do you squirt or release it under the surface of the water? Goldfish are very well known for swallowing too much air.

At my store, this used to happen all the time. (We now inject the flake food under the water surface with a turkey baster.) When it did, we would take frozen peas and thaw them in warm water, deshell them, and let the goldfish eat them. Within a couple days, they had managed to deflate themselves and were back to normal. I'm afraid the reason for this working is still unclear to me, but I believe it was because the extra fiber in their diet helped expel the infection; or else, they just became gassy and passed the excess air :P

Like I say, the reason is still uncertain, but we used this method many times with success.

Also, to the other commenter: these goldfish are supposed to have about a twenty year lifespan and attain a VERY large size (six inches, I believe, is average). It was stated this one is approximately golf ball size, so his age- which is most likely not too high- should have nothing to do with his illness/peculiar behavior.

Sounds like he's sick, or on his way out.

There's never a really good way to tell how old a fish is, unless you're buying direct from the breeder.

Fish don't usually "play dead"