Bullying in goldfish

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Aquarium Advice Newbie
Mar 4, 2022
Hi all,

I currently have 2 fancy goldfish (a black moor and I'm not sure what type the other one is but it has an egg shaped body and is definitely fancy rather than common) in a 94 litre tank. They have been together for around 18 months and until very recently got on very well. However, for the past month or so, the unidentified fancy has started bullying the black moor. He chases and nips at the black moor a lot and recently the black moor had torn fins due to this. I put a tank divider in there to help the black moor heal, but I realise this isn't a long term solution. The black moor healed well so I took the divider out yesterday but the nipping has started again. Nothing has changed in the tank over the last month at all, however the unidentified fancy has grown bigger than the moor since I bought them.

Water parameters are:
- 0 ammonia
- 0 nitrite
- 40 nitrate
- 7 pH
- 0 KH
- 30 GH

25% of the water is changed usually once or twice a week.

I'm concerned that perhaps the tank is too small, which would be so upsetting. I bought way bigger than the pet store said I would need to try and avoid having problems. I adore these two fish so any advice you can give me would be amazing.

Thanks in advance!
Last edited:
Welcome Goldie28!

It is SO frustrating that the store people give inaccurate advice.

As for the tank, a 94L would be 28.8G And a much too small tank for full grown fish. I can't even imagine what size they recommended would be fine.


Check a look at what size your fish could have aspired to be! It is truly difficult to understand that a little 2-3 inch / 7.5 cm fish could have the ability to be a softball in around a year!!! Granted those are usually show fish genes, but I think one pic was just a regular fancy GF from the store.

They can bully / harass their tank mates. And I will check for the thread which discussed putting the fish in a time out net and training it that the behavior is not acceptable in the tank, :). I haven't used that for a GF but I did do it with some other fish I forget at the moment which one and after a few times it stopped bothering the other fish.

Other things could be the water parameters are out of the safe zone, Ammonia, NitrIte and Nitrate. If the water parameters were checked before the pwc, then You would have the most accurate measurement of what is going on in the tank. And just checking if the water parameters were checked at the time before a maintenance pwc, or after?

They could be arguing over dominance. One could just be a big jerk.

You can try removing the biter for a day or 2, and rearrange the tank, even if you plan to put it back the way it was (take pics to remember how it looked, lol).

Adding some long stem plants, even plastic ones, to break up the areas somewhat.

The adding the biter back into the tank, and in theory, the tank would be now the one that got bit's domain. Sometimes that works, and sometimes it could be a jerk fish who doesn't play nice.

How big are the GF now? Boulder Marble, Ping pong ball, Golf ball, baseball sized?
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