Why did my goldfish eat my smaller goldfishes tail?

Question

could you please help me please answer my question

Answer 1

he was hungary.  And said give me your tail.  

Answer 2

GOLD FISH EAT OTHER SMALLER GOLD FISH. REMOVE HIM TO ANOTHER TANK. GOLDFISHES ARE FEEDERS  

Answer 3

Cause he's the new guy.

Answer 4

It'll grow back in a matter of days. Did you check your pH and ammonia and stuff? How big of a tank do they have? If its a gallon tank put them in a 20 gallon tank, they'll get stressed and most likely eat each others tails.

Answer 5

Some more information would be appreciated. Are they in 30+ gallons of water? If not, they are getting territorial because their aquarium is too small so they chase each other and bite each other. Goldfish are normally peaceful fish, so this aggression is rare unless something is wrong. Is the smaller fish new? Your established goldfish is angry someone else is in his territory. You need to rearrange the tank decorations so established territories are eliminated. Are they the same type of goldfish? Commons and fancies should never live together. Commons are generally more aggressive when it comes to food and territory. Fancies because of their body shape have a harder time swimming for food and running away.