I can't believe I am asking about this but.....do fish have 'seasons'?  You know, like dogs?
We have 4 fish and they are all going crazy following one fish around the tank.  I swear, I feel like taking the little' un out the tank till they calm down.  It must be exhausted!!  They are shooting around all over the place and the smaller one (i think) looks like it is trying to hide but the rest are not giving it a minute.  Poor little fish.
I'm only asking cos I'm curious.  I'm not about to turn 'fish breeder'!lol

No they dont have seasons but they lay eggs you will see them all over the tank if they arn't eaten first.

Ahh, I have seen little sac things in the tank.  Oh, Am I now a fish breeder?lol!
The little girlie one(so I now think) is hiding behind the filter trying to get a bit of peace!  And the other 3 are still looking for her!

My goldfish that were in a very large tank laid thousands of eggs. We took them out though as the big fish were eating them and fed the fish when they hatched on the little water fleas. Loads of them survived and we ended up giving them away.

Sometimes Goldfish can bully other fish in the tank and that's what this sounds like to me.

The fish being bullied could possibly be unwell.

If it was me I would take it out and put it in a separate bowl for a while and see how it goes.

You can actually sex goldfish if you have a keen eye, females have a very small bump just next to their vent and they will appear slightly fatter.  Males have a completely flat vent and can have small white dots on their gill covers and on the longest edge of their pectoral fin when they are in breeding condition. 

In the wild their breeding season would be spring but in a tank it can be any time of year if the conditions are favourable. Your fish must be very happy with the way you keep their tank and the amount of space you have given them.  I would just add to make sure you have a lid on at all times, when things get very frantic the fish can jump out.

It was definately some sort of breeding act as we spotted eggs in a sac later on which one of the other fish then ate! Yuck!  but I do put a bit of faith in your bullying thing too.  The main 'chaser' is quite a territorial fish and is seemingly quite aggressive.

Funniest thing ever?  My 11yr old cocker has only noticed today that we have fish and she has tried to climb the unit to see them better!!lol  She's been dangling off the sofa edge and everything totally enthrawled!  We've only had them for about a year!!haha

My knowledge of how fish breed is rather sketchy, but I know in some species when the female lays her eggs, the male has to spray his sperm (milt) over the eggs to fertilise them.

Logical thinking.... if goldfish aren't the kind that do that, then they must have been 'mated' before the eggs appear in order for them to be fertilised. While I have never seen goldfish in flagrante, it could happen. or not!

So in the absence of the finer and more delicate points of goldfish reproduction, the 'aggressive' male may just be trying to fertilise them as they are laid?

> So in the absence of the finer and more delicate points of goldfish reproduction, the 'aggressive' male may just be trying to fertilise them as they are laid?

This is exactly how they do it.

Yes, the little fish sort of squatted in the pebbles and then the bigger fish went mad for that spot.  She finally got peace!
Today, the tank is a lot more subdued, thankfully!  Fish are supposed to be relaxing!lol

Really still laughing about that daft old cocker just noticing them!!lol.  She's such a dosy old lady these days!!haha.
My cousin came in the other night for a visit and sat on the sofa right next to her.  She was in for half an hour, cuppa and a chat and the old cocker didn't even know anyone had came in! God help me if that had been an attacker!lol

> My knowledge of how fish breed is rather sketchy, but I know in some species when the female lays her eggs, the male has to spray his sperm (milt) over the eggs to fertilise them.

This is indeed what goldfish do.  The males chase the females around almost constantly, pushing them through things like plants until the female lays the eggs then the males are right behind to fertilise them.

It can be exhausting for the females and in a tank could actually kill her so if they really aren't leaving her alone at all then I would definitely separate her, but make sure she has a decent setup with a filter etc because she'll need a clean environment to recover.  Just putting her in a bowl will stress her out much more and tax her body as it won't be as clean or well oxygenated.

Also if you can lower the temp of the tank that will help as it's a temperature rise (i.e. spring) that triggers the breeding season.

they will probably breed again every few weeks for awhile usually the day after you've changed their water.
my guys quite enjoyed watching my fish as well don't have any at moment must get some i miss watching them as well it's very relaxing