Hi,

I was wondering if anyone here could offer some advice on this. I started a new 20 gallon aquarium and introduced 5 leopard danios (3 females, 2 males) to help cycle it. I added 2 older and larger zebra danios (1 male, 1 female) a week later.

One of the female leopard danios started to harass the zebras after about half an hour, even though it was much smaller. It didn't just chase them around... it seemed to be attacking them by nipping at their sides constantly. It also chases some of the other leopard danios around. Should I remove her from the tank? Is there such a thing as a non-community-tank danio?

Thanks.

I never had a "bully" danio like that but I've heard of them. You have enough fish that no one fish should be picked on. My danios have never hurt each other so I find it strange that you say the bully is actually nipping. It's up to you whether you want to separate her or see if she changes over time.

Hi Robyn. I've already taken out the zebras since the aggressive leopard would not stop hounding them. I also plan to keep watch over how she is to the other leopards. Hopefully she won't be a problem when I add some other fish in the future. If she is, then out she goes.

Thanks! :)

I have a school of Zebra and Leopard Danios in a 55 gallon tank. One Leopard is quite a bit larger than the rest, but I have noticed no excess of aggresion. Perhaps the twenty gallon tank isn't large enough. If your Leopard is trying to establish dominance over the school; could this cause the extra harassment?

I've noticed the same thing with my Danios. I have one leopard, 3 Zebra and one Pearl. I don't think this is a good combination, but do not have the funds to buy another aquarium to separate them. The Leopard Danio is constantly harassing and pushing around the other fish. They all have to hide. The Leopard with actually run into the other fish and seems to be nipping at their tails. I haven't seen any actually nipped fins, but my Leopard Danio is definately the King of the tank.

Danios, by nature, are seemingly aggressive. They will chase each other around, and sort of nip at each other. It is rare, however, that they will actually hurt one another. Having different types of Danios in a single tank is not a bad combination at all. I have Leopards and Zebras in the same tank, and there is no problem.