Rasbora on the way out

[fishfanatic2]

My last remaining rasbora heteromorpha that I have had for 6-7 years seems to be on the way out. He's swimming at a 10 degree angle upwards without much energy and occasionally loses balance and barrel rolls or goes upside down. I think the most likely cause is old age, however the tank has seen a bit of neglect recently and I want to make sure that its not something else that could affect the tank. No external signs of disease, the only thing I could think of is oxygen depletion, but he isn't gasping either. Is there anything else there could be?

 

[Anonymous]

old age- put it out of it's situation