The circle of life is beautiful but so sad in the end unfortunately. A few of my fish have aged out recently. I could see it coming on very similar to elderly senior citizens to. They just start to slow down more, needing more naps and rest, starting eating less as their body slowly shuts down. They were so energetic before. I had the hardest time some years back when I lost my 16 year old datschund. Like losing a family member. Now I'm sitting here watching my midas blenny complete his circle of life. He used to be the most active fish in the tank to. Just a bummer day coming on.