Eating: interest matters more than quantity
An old fish that still comes looking for food, watches the surface at feeding time, and manages its usual meals is holding onto one of life's main pleasures. The slide is gradual: meals approached slowly, then picked at, then ignored on odd days, then refused altogether. A fish that has not eaten for several days running, in a tank where the water tests fine and tankmates feed normally, is telling you something important about how it feels inside its own body.
Movement and rest
Watch how the fish holds itself in the water. Healthy old fish are slower, but they swim level, rest in favourite spots, and can still rise to the surface without struggle. Failing welfare looks like constant effort: sinking or tipping when it stops swimming, a spine that stays curved, long hours lying on the bottom in odd places, or wedging into decor for support. Resting more is age; being unable to rest comfortably anywhere is suffering.
Breathing and body condition
Breathing should be unhurried. Gills working hard at rest, gasping at the surface in well-oxygenated water, or one side moving less than the other all signal a body struggling to cope. Look, too, at condition over weeks: slow weight loss despite food offered, wounds or fin damage that no longer heal, growths that keep enlarging, eyes clouding. An old body repairs slowly, but injuries that only ever get worse mark the point where time is no longer on the fish's side.
Engagement with its world
The subtlest sign is interest. A fish with acceptable quality of life still notices the tank: it watches you approach, reacts to tankmates, investigates a moved stone, comes to its feeding corner. Withdrawal — facing the back glass for hours, startling at everything or reacting to nothing, hiding through whole days it once spent in the open — suggests the fish's world has shrunk to enduring rather than living.
Keep a good-days and bad-days record
Memory blurs decline into a feeling that he seems worse lately, which is hard to act on and harder to discuss. A simple daily note — ate well or refused, swam or lay all day, interested or withdrawn — builds an honest pattern within a fortnight. Mostly good days with a bad one after a disturbance is an old fish coping. Bad days outnumbering good ones, week after week, is the pattern that means the kindest conversation is due.
Talking it through with a vet
Bring the record and your water results to an aquatic vet. They can check for treatable causes behind the decline — sometimes water or a manageable condition is masquerading as old age — and talk honestly about comfort and, when the time comes, the gentlest options. That is a conversation to have with a professional who knows the fish's history, not a decision to carry alone at midnight.
Writing those daily notes into your old fish's Pet Passport on KinsLe keeps the good days counted as faithfully as the bad ones, so the picture you act on is the true one.