Zebra Danios swimming at surface when lights are off

[RobScoots]

Hello,

So I have a question about the nocturnal behavior of Zebra Danios. It seems every time I leave them with all the lights out (as in all the lights in the room, not just the tank lights) for any significant length of time, I turn on the lights to find most of them swimming at the surface. Of course, this always freaks me out because I assume they are gasping for air, which it appears they're not. Usually once the rooms lights are on for a minute or two they start swimming around the tank again and don't go back to the surface.

I have plenty of aeration and good surface agitation, so I don't think O2 is an issue. My tank is cycling and I've been getting some NitrIte readings, but I've been on top of the WC and prime, but it has me concerned that that could be an issue. But it only seems to happen when the lights are off, and then quickly stops once they're on.


Is this normal behavior? I guess it could be a normal nocturnal instinct, but curious if anybody with more experience could let me know what's up.

 

[codygregg]

I have 8 Zebra Danios and they do the exact same thing! I always thought it was weird but never really worried about it. They seem to be healthy.

 

[kemar]

Its a naturally evolved reaction. In the wild when its bright and sunny they are more visible hence more prone to predators therefore they stay hidden or below unless they feel really comfortable. When the light is off they feel safer and roam about more(not nocturnal). My danios used to go crazy in the shade

Sent from my TM-5377 using Aquarium Advice mobile app

 

[martintanks91]

Zebra danios are top dwellers, they always Stay at the top, i have 8

 

[BlaxerGun93]

Yeah I used to have Zebra Danios. They would always swim on top.

 

[minnowbouy88]

Defiantly a natural occurrence my zebra danio's are always on the surface of the water when all the lights are off, both them and my white clouds are all night time surface sleepers. Sounds too me like they are happy as they are acting normal