Danios Glofish Sick? What Can I Do? (Video)

[gabriel.mihu]

Hi,
 
All my fish that behaved like the glofish in the following video ended up dying (2-3 of them, last one about two weeks ago). When he swims, he's ok, but when he stays in one place, it seems he cannot "keep his balance" and he needs to readjust all the time. I don't know what's going on, so any help is useful. Previous fish usually died in 1-2 days after starting to behave like this.
 
Here's the video link:
 
http/www.youtube.com/watch?v=GYSEGWXWQ6k&feature=youtu.be

 

[fluttermoth]

How big is the tank and is it cycled? Was it a fishless or fish-in cycle and, if fish-in, was this one of the fish that went through it?
 
Have you tested the water and, if so, what were the actual numbers? What temperature is the tank at? Any other fish in there and, if so, what kinds and how many?

 

[gabriel.mihu]

36 gallon, cycled, about 10 weeks old. Fish-in cycling, cycled in about 5 weeks. This fish was added at the end of cycling, and has been in the tank for about 6 weeks.
 
Last test was last week, ammonia <.25ppm, nitrites <.25ppm, nitrates <10ppm, everything has been constant for a few weeks now. Yesterday did a 35% water change. The glofish behaved the same before the water change. Temperature 77F +/- 1. The other fish that died the same way: about three weeks ago, 2 silver mollies and 2 male guppies - they died the same day I brought them from the fish store... they had some issues with them, as all of them died in a few days in the fish store; one of my yellow glofish died about three days after.
 
All fish:
9 tetra neons
2 green cory cats
4 guppy 8 weeks old
1 male guppy
1 platy
4 danios glofish

 

[dave840f1]

I think if you had a water problem the Neons would be the first to show signs of a problem.