Not sure if he's poorly or not, he's missing a pectoral fin! I've only just noticed so he could have been missing it for a while, neons are so small and the fins are almost clear! Could he have been fighting with another tetra, they have all been playing tag a lot in the past few days? Other than that he's eating and doing what the rest do! I've had my fish almost 3 weeks and the ammonia, nitrites and nitrates have all tested 0ppm up to now