Bye Bud, I'll miss you

#1
I just lost my Opaline Gourami a few days ago:( He was a great fish and I had him for about 3 years. I always noticed that whenever I did a water change he would kind of change shades, but one day I noticed his front half was lighter blue and his back half was darker blue, with a obvious stopping point, you could literally draw a line down the fish. and He was like that for like 2 months and still eating and fine and I asked all the LFS and stuff and they had no clue, so I just made sure the water levels were perfect and all, and then he just died one day:( .