Unusual Occurance In My Diamond Tetra

[Charzendat]

Hello. You guys have been helpful before and I ask for your help again. I have a 30l tank which contains 6 tetras (4 diamond and 2 glowlight). I just fed them and noticed one of my diamond tetras looked a bit off. His body is more opaque than the others and he has an unusually string like thing coming from his body. Also he is staying close to the bottom of the tank and while he is swimming around he does so quite slowly. Also his mouth is moving quite rapidly and constantly and his body is slightly bloated. I can see no evidence of an attack and there are no apparent issues with any of the other fish. Does this sound familiar to anyone? If so what (if anything) is wrong?

 

[SlyPolak]

unusually string like thing coming from his body.

Is it coming from his bum?? Does it look like stringy poo or is it located somewhere else....

 

[Charzendat]

No. It was white and coming from it's underbelly, in between the front fins. Anyway it has fell off now and while he is still a bit off colour and off food appears to be ok. Thank you anyway.