Neon Tetra Sickness ID

[Deadna]

So, I recently purchased 15 neon tetra and a flame tetra (the idiot at the store grabbed it). One of the neon tetra is looking strange, with a completely faded red underbelly, and faded green stripe. Also, he is swimming off by himself at the bottom of the tank. Any ideas? Thanks!
Also, the tank belongs to a younger sibling of mine, and it is his first tank. I don't believe it's done cycling, but he hasn't tested it in a while.

 

[PB_Smith]

Just from the pic it looks fine. Neons coloration does fade at night and it can take a little bit in the morning before they color up. I have seven and they go through periods of all hanging together or going off on their own.
One other thing that greatly influences the coloration is the substrate.
Darker substrates will show off the colors much, much better than light colored substrates.
As long as it is eating good, I wouldn't be too concerned at this point.
but you should get the water tested to make sure it is done cycling.

 

[Delapool]

Yes, can't see anything there. One to keep an eye on though if he doesn't rejoin the school.

 

[Deadna]

Well, he died. Found him sucked to the filter. The tank is competely cycled (0 ammonia, 0 nitrite, .5 nitrate), I guess he was just sick/old/dying when we got him. Thanks for the responses.

 

[Delapool]

Sad news Perhaps he just couldn't adjust.