Neon Tetra Sickness ID
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.