How (if you can) tell if a fish is dying from illness or old age? For example if the fish you bought at the fish store was already old, but you didn’t know.
I don't know any fish for which this is always accurate. Sorry, can't let that stand.As a fish ages their scales change, if your fish have dark edges on their scales, then it is an old fish. Young fish have bright scales, older fish have duller scales with black lines on the edges.
It applies to all fish if you look closely at them.I don't know any fish for which this is always accurate. Sorry, can't let that stand.
It depends very much on the species.
- A cardinal tetra will become paler coloured, with more white colour spreading from the stomach. Speaking of which, the stomach may become bigger or the fish gets thinner.
- An Apistogramma will also become thinner, the fins may grow all live and thus become oversized and start to curl or bend. Also these fish can become grey.
Other possible signs of old age: Blindness (cataract), less activity, slightly bend spines (like a hump or a caudal fin hanging down a bit limp), unusual slightly tilted swimming angles...
Generally one thing that shows if a problem is age related or genetic, is simply when bodily functions (buoyancy, digestion, responsiveness) stop working correctly without typical signs of illness: No loss of appetite, no loss of social status, no reclusiveness, no other outer signs.