Hello everyone. Recently I bought 10 Neon Tetras from Petco. I was examining them when I noticed one looks a little fat in the front and picked clean in the back. I'm not sure if this is my eyes playing tricks on the vast size difference, but he looks bad. I tested Petco's water and the ammonia was .25 ppm. not sure if that would make a difference but I made sure not to let any of it out.
I'm including a picture of this and I hope someone can tell me what this looks like. also what I should treat for, or if I have to...euthanize.
Pic is blurry but you can see half his body is messed up