Red Eye Tetra Problems swimming

In the last few days one of my Tetras seems to be sick. He can't keep his tail up and swims with is mouth up, almost vertical. He does not appear to be eating either. Everytime he looks like he trys to relax he starts to fall to the bottom then, stuggles to stay at the top. I have tested my water and everything (pH, Nitrate, Nitrite, Ammonia, temp) are all normal and at the same levels they have been for months. All of my other fish appear fine and my sick tetra other than being unable to swim has no outward signs of sickness (spots, growths, etc).

Can anyone help me. I am worried that it is probaly too late for him, but I am not sure if there is anything I can do.

Thanks,
Jeff
 
jmottle, no answers in two days, I think, because we were all daunted, and nobody liked to point out that these symptoms are terminal death throes. When basic swimming balance is lost, a fish is on its way out.

The "cause" may be multiple, rather than one single thing, such as liver damage from exposure to nitrites months ago. Summer heat was a contributing factor for the bacterial infections that recently did in a male Badis ruber in one of my tanks, for instance...

I try not to let fish actually expire in the aquarium. Any sporidean parasites it may be carrying are released after death, and other parasites can be transmitted when a fishes' tankmates scavenge it.
 
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