There are so very many grey/silver fish that are similar to goldfish. It is probable however that you are refering to a goldfish that has not coloured up. Goldfish are all silver as youngsters and only develop their colouring as they grow older. Some stay grey/silver and never develop colours.
They are fish in the carp family genus Carassius. Specifically Carassius auratus.
A carp is a giant goldfish, with a variety of colours from black through to white.
the great gold fish
Carp
a carp
Koi
a golden fish. that's about the simplest explaination.
The fish is pooping.
You could go by the golden rule. If to all intents and purposes it looks and behaves like a goldfish, in all probability it is a goldfish. Goldfish come in very many different shapes, sizes and colours.
If you mean like a Siamese fighting fish or beta fish they are like.. size of a ordinary goldfish I think and can be many colors but the fins are long and wavy it's a very elegant fish but still has the intend to kill another fish. But these are only the males. The females brownish maybe goldish. Not as flowy on the fins and looks for like a goldfish. ;)
Asterophysus batrachus, the Gulper catfish, has such a large mouth that it looks like a smiling fish.
Your fish might be getting fat, you should not feed it as mutch if that is the case you will be fine.
Goldfish.
Goldfish have a backbone, like all fish, which does indeed make them invertabrates.
la snow fish looks like you
Earthworms and baby fish
No, they can not. Fantails are goldfish and goldfish like temperature from 63-750 . And no goldfish can not be with any tropical fish. It can only be with other goldfish they are likely to nip a little to pick on who's weak but it is not a problem.