How can you tell if a goldfish is sick?

[Im a Manatee]

I'm in charge of taking care of the class' goldfish, and I think it's sick or something.

It stays in the corner of the tank, swimming up and down against the corner.

Odd?

[invincible rob]

Nope, or at least i shouldnt think so, you only have to worry when a goldfish keeps tipping on its side and floating to the top (that means it doesnt have the strength to maintain balance).

[Maka]

The fish may be blind, and be trying to use it's other sense with arent working. Or it's scared of the other fish within the tank as they "Bully" it if they're bigger. As long as it's not swimming upside it's probably fine ;) It's a fish

[Cola Alone]

http://afcg.com/archives/images/Goldfish/smal_1.jpg<---- bad sign.

[Im a Manatee]

Heh, he's the only one in his tank, It's a bit cramped.