I have a fairly heavily planted 10 gallon aquarium set up, and I currently have 3 zebra danios in it. When I went to the LFS
the day I got them I wasn't planning on getting danios but the LFS
guy talked me into it and now I sort of regret it because I now realize that they like to be in much larger numbers than 3 and have more swimming space than a 10 gallon.
I plan on finding them a proper home, but in the meantime they've all been healthy and active.
However, I noticed yesterday that one of them is just hanging out at the top corner of the tank floating there, not really swimming at all. If startled, he'll dart around normally, and if the other two come close he'll chase them away, but he always comes right back and sits there at the top out of the light.
When feeding, he'll come and go after food voraciously, but I don't think he's actually eating, seems like he's just biting and releasing.
I'm not sure what's wrong because he doesn't really look visibly ill.
The tank is fully cycled and yesterday it tested 0ppm of ammonia, do you guys know what may be the problem and how I could possibly cure him?