Aggreaive zebra danios.

[Jake_71]

I have a 10 gallon fresh water tropical tank. 1 black Molly 1 blue powder dwarf gourami and 3 colored zebra danios. I did have 4 zebra danios but one died for an unknown reason recently. But since then my blue danio (the biggest one) has been attacking my purple one (the smallest one) there is another yellow one that follows my blue one around and they seem to get along. But every time my purple one gets close to to my blue one the blue one he would chase the purple one until he hid in my log or behind a plant. I know these fish "play tag" they all use to do this until my red one died. Now my blue one is being very aggressive to my purple one not any other fish though. So do I need to get another zebra danio or will my tank then be over stocked? Please help I don't want my purple one to die he is a great fish.

 

[DavidAl]

Hi Jake,

Zebra Danios are very active fish and should therefor be housed in at least a 20-gallon long, and your molly will require a bigger tank, too.

Anyway, zebras have been known to harass fish with no end in sight, even their own. As you're seeing, they are extremely energetic and will chase each other until one decides to hide. This is all too common. A bigger tank with lots of hiding places would serve them well.

Their chasing around will usually not lead to death, so I'm surprised to hear that the red one died as a result of the blue one's aggression. I think this would all be resolved with the addition of more zebras, but only in a bigger tank.

David

 

[Jake_71]

My red one did not die from my aggressive blue fish, I don't know how he died he was very active. But they all used to get along until the red one died.

 

[Jake_71]

Update. When I turn on my blue LED's and turn of my white ones the zebra danios start schooling again with no fighting! But short after I turn on my white lights my purple danio goes right back in the log to hid knowing he will be attacked. Here are some pictures. Is it because they can't tell the difference in colors of other fish because the blue LED's turn everything blue? You can even see when I turn the whites back on the blue one is rapidly chasing the other. Not in a peaceful way.

 

[DavidAl]

Fish tend to stick closer together at night to avoid predation. To the predator, they don't want to look like a single fish, which can be seen as a sick fish, but as one big fish, which is more likely to be the case if they are huddle up tightly. Along those lines, if they're chasing each other around in the dark, it would expose themselves to the "predator." And that's why they don't do it when it's dark (blue LEDs).

This is also why many fish lose their bright colors at night, only to return when the lights come on.

David

 

[Jake_71]

Very interesting info. Thanks for that. I almost never use my blue lights but I am going to use it more because I left them for an hour with the blue light on and I turned the bright one on thinking it would get ugly between the two fish again but it didn't. Maybe this light will cure my angry fish.