A goldfish has a memory of 3 seconds so when it starts to eat itself and it hurts, it just forgets and does it again.

That makes no sense.

Sure, the memory only lasts three seconds, but the discomfort or pain that comes with a gut stuffed full of fish food to the point of killing you doesn't go away.

He still feels it, he just forgets that it's been going on for more than 3 seconds.

It still should trigger some type of "I better stop eating" reaction.

No. Your wrong. I have spoken.

Most goldfish suffer from weight problems. Most see themselves as fat slobs. By eating themselves, it accomplishes 2 things: 1. They eat fish, which is lean and has protein, and 2. By eating themselves, it really does make them thinner. The real problem is all the goldfish magazines that show skinny goldfish swimming down the runways, which makes all other goldfish turn to the extreme measures like eating themselves to look like the goldfish models in the magazines.