Black Phantom Tetra Swimming Oddly

[james1971]

I have had 4 black phantom tetra for about 3 months now but in the last week one of them seems to be swimming oddly. He moves around the tank with slightly 'jerky' body movements as opposed to his friends who just glide around. He does seem to be slightly smaller than the other 3.

I cannot see any signs of disease or damage so I am at a loss as to what it could be. He is not getting any worse and seems happy enough - he is still eating OK - I am just a bit worried about him.

Anyone had a similar problem ?

Any advice would be welcome.

Thanks

James1971