long fin barb - looks to be dieing

[miketech]

long fin barb - looks to be dying

Long fin barb has been losing color and fins within the past 4 weeks. He/she is maybe 3 years old. Has been staying at the top of the water near the bubbles for the past week. Eats fine. Comes to the glass when I get close. Has gotten smaller over 3 weeks.

The other long fin looks worried...it goes up to the (possible) sick one every few minutes. Could it be some type of disease? Or is it caused by age?

Thanks for any advice.

Pics are attached. The last picture was from over a year ago.

 

[miketech]

I never have cleaned my filter tubing within the past 2 years. Did that yesterday. The Nitrite is at 0, the other Nitrite is 30. The Amonia is at zero and the PH is at 6.1. PH level has been stable for over 6 months...I tried buffers before but all they do is prevent the water from being crystal clear it seems.