Fish chasing another fish butt?

Question

I have a 44 gallons tank with a few kois and 3 comet goldfish. One of the goldfish is really big (my brother raised it). I don't know if it's a male or a female. Anyway, recently I notice the other fish (koi and goldfish) started chasing this goldfish and bite it in the butt. Is this mating or should I be worried about something else? How can I tell? Thanks.

The thing is the big goldfish has been living in the tank for a while now (may be a month or more) and this didn't occur. The koi are very small so I'm not too worry about them growing big just yet. I plan to have a pond eventually.

Answer 1

They are feeling threatened and are ganging up on him. They will nip and peck until they kill him if you leave him in that tank.

Answer 2

Hi CT, I think what you're seeing is normal mating behaviour. Have a look at the fish doing the chasing-chances are he has tiny white specks all over his gill covers & perhaps along the front rays of his pectoral fins & the semi-circular plate around his eye too? These are called tubercles & the he uses them to rub against the flanks of the female to stimulate egg laying. Often it can get quite boisterous & go on for hours, especially with larger fish & sometimes minor damage may occur like missing scales or split fins (& not just the females!). Make sure you have provided some places in your tank for the females to rest & hide.

By the way-I wouldn't leave it too long to build that pond otherwise you may need a 200 gallon tank sooner than you think!

Answer 3

Theyre chasing after some tail lol. No, seriously the goldfish needs to be in another tank, the other fish will kill it.

Answer 4

i agree with the other woman, are you sure you dont have too many in your tank? 1 inch of fish for every gallon of water. since koi's get huge and i know 44 is not THAT big.

Answer 5

I wouldnt worry to much probley just being a little tertoraly and letting them know whos boss they probley learned there lesson

Answer 6

Butt?