Goldies are typically not agressive. The most aggressive behaviour is during spawning. Males will chase a female and bump her belly to cause her to release her eggs. Goldfish are egg scatterers which means the female drops her eggs all over the place as she swims along, she does not lay them in one place. The male then swims behind her and fertilizes them.
Sometimes if you have several males and one female ready to lay eggs they can get quite brutal and stress her from chasing. If you can move her to another tank or I have found the small plastic storage bins (with holes....looks like a small laundry basket) works great! Just float it in the tank and put her in it to let her rest if she is stressing or her tail is ragged from the chasing.
Chasing the Sun - 2001 All Aboard 1-4 was released on: USA: 2001
the goldfish that is being chased might be a female goldfish where as the others are male goldfish, so the female one gets battered around the tank and the fins and tail might shred it is a good idea to separate the single fish so it wont be attacked. i know this cause my Goldfish do the same XD Look for white dots on the cheek of fish that r chasing the other one. if it does have white dots its a Male hope that helped :)
Chasing Farrah - 2005 Still Farrah After All These Years 1-6 was released on: USA: 20 April 2005
Depending on the type of goldfish they can be anywhere from 6-12 inches long.Try the article at the website in related Links It is all about goldfish sizes
Snorks - 1984 All That Glitters is Not Goldfish 4-28 was released on: USA: 1 December 1988
All Goldfish make great pets provided you give them good water and food. Remember the basic rule of '1 inch of fish needs 1 gallon of water' then remember that your goldfish will grow to at least 12 inches long given good conditions.
Chasing Life - 2014 Pilot 1-1 was released on: USA: 2014
Chasing the Saturdays - 2013 UnitedSatsOfAmerica 1-1 was released on: USA: 20 January 2013
Chasing Life - 2014 1-2 was released on: USA: 2014
Chasing Life - 2014 1-3 was released on: USA: 2014
Chasing Life - 2014 1-4 was released on: USA: 2014
Chasing Life - 2014 1-5 was released on: USA: 2014