I hav had this goldfish tank for around a year now....some of my fishes hav begun 2 act strange lately....3 particular fish-a redcap,a shubunkin and an orange goldfish(kid)- attack one of my other orange goldfishes(say 'smarty')....it strted about a mnth n a hlf ago, when they wud chase smarty all arnd the tank ....of late i find the 3 trying to push smarty onto the ground....the incidents hav begun to occur more frequently over the last couple of weeks.....smarty seems quite helpless against the attacks....its always the same 3 fish attacking smarty...moreover,(i find this quite amusing actually), those 3 fish seem to hang around together!!!

Any suggestion??? (apart from removing smarty or any other fish from the tank)

Smarty n redcap hav been in the tank all along....shubunkin n the kid came around 5 or 6 mnths ago....

What size tank and how many fish do you have? I'm wondering if overcrowding could be leading to the bullying behavior that you're seeing. Has smarty sustained any injuries?

@natalie...

yup the tank is a bit crowded....but why this sudden aggresive behavior???n is smarty really in danger, or will this continue for sum days n thn everythn will b alryght???

@Alasse...

its a bit embarassing 2 admit it, but m not sure about their genders....even the aquarium guy sounded vague whn i asked him....he just said the females r a bit more "rounder" thn the males!!!...how do u determine a goldfish's gender???

How big are they?
Males get tubercles (white pimple looking dots) on their gill plates and often on the pectoral fins, though not always easily visible.

The males nudge and push at the females to induce spawning, she will not spawn without this, being young the males may be practising and the female may not be ready.

My fantails aren't very big and they a definately displaying the same type of breeding behaviour.

What size of tank Do you have ? is it a 18 gallon thats what you put for size? And how many goldfish do you have in there?