Is He Sick Or Just "different"

[barb-e]

First the history of the tank: I have a ten gallon tank. It currently houses about ten white cloud mountain minnows. I bought the first set of wcmm's about two years ago and unfortunately, they died one by one until there was only one left. I don't know why the others died but the survivor has held on no matter what. He lived in the tank by himself for a few months and a few months before all of the other fish died, he started swimming kind of funny. To get to the point, I added six little buddies to the tank about seven months ago to keep him company. He swims around with them, he eats with them. However, he still struggles a lot to get around and he often just collapses and floats on the side, I have though many times that he was dead but he always swims away after I watch for a while. I don't know if he is suffering or not. He is very skinny and pale but he is still active. I noticed a weird looking bulge on his side today. I don't know if I should just let him be and live out his life peacefully, though differently from his tank mates, or if I should consider humanely euthanizing him. Any thoughts?

 

[loraxchick]

is he eating ok? spitting out food? ever dart or scratch against objects in the tank? Have you noticed his poo (white/stringy/mucousy)? what is his diet/feeding schedule?
Might be internal parasites in which case you need to medicate. His abnormal swimming is likely a swimbladder problem can be caused by a wide range of suspects. som more info would help. a picture would be great!
cheers