Bully fish

[Maria94]

Hi all,

I have 2 zebra danios in my tank for cycling.

One of them is so mean keeps chasing the other one when he tries to go near the top of the tank!

Is this because of where the food is? Or is it because I'm supposed to have 6. I will of course eventually but, whilst cycling it's way to much of a bioload. They've been together 4 days and it only started yesterday morning.

Starting to stress me out! Not a good start to fish keeping!!!!


Thanks in advance!!!

 

[fluttermoth]

Yes, it's because you should have more. Zebra danios form quite a complex hierarchy and, if kept in inadequate numbers, it's easy for one fish to become a bully.

It would be best to rehome/return the danios and do a proper fishless cycle.

 

[Maria94]

I've noticed they don't do it after food, or when I turn the light off?

 

[Byron]

To expand a tad on what fluttermoth posted...this is a shoaling species of fish. Most all the barbs, danios, rasbora and tetras are shoaling, and many others are too. This means that evolution has imbedded the fish through their DNA to expect a large group. When this is denied them, they are stressed, and most fish react by increased aggression to each other. Think of it as frustration, and it is about the only way a fish can respond to frustration.

Fish can be individuals just like any animals, so things can be different. But providing the "norm" for a species is always going to lead to better health. And, what we may see as "play," is usually much more serious to the fish.

While everyone always needs to know the minimum because of tank space limitations, we must remember than more than the minimum is always going to be better because it is a bit closer to what the fish expects. Six will work, but seven would be much better, and eight better still. I don't know the tank size, and six may be all you can have, but at least you now understand why you are seeing the behaviour you are. And this needs to be addressed soon, because over time fish can be internally affected by stress, leading to more problems.

However, the cycling issue is in the way, so clear that up first.

Byron.