One of my neon tetras doesn't look right...he is swimming at a 45 degree angle (up) constantly, unlike all the other tetras who swim in a straight line. He is very spazzy moving all over the tank. The other fish are also swimming around but in a much calmer manner. I can't tell if he has a damaged fin because he is so small and jittery. His swimming pattern does not affect his ability to get out of the way of other fish or to swim for food...but its still bothering me because it looks so awkward and uncomfortable. Does this indicate a health problem or something?