Its really a jugment call the longer you have fish in a tank, or choose to breed fish the more knowledge you will aquire in being able to determine to some degree how old a fish, or school of fish might be,if a fish looks old it probaly is, length and width will get you somewhat close combined with a good close once over visual. If you have any fish books you can find what type of fish you have in the book and the book will tell you every thing you need to know how long the fish will get when it gets to a mature age. Some fish live a long time.
A one human year old goldfish, is eighteen goldfish years old.
Comet goldfish are the average pet, although you can now get funnier types such as (my favourite) Celestial goldfish.
If it is as old as a goldfish that can, it can.
Normally goldfish are peaceful and calm.But incase your goldfish is doing so then its better to separate the new goldfish.
43 years old
well it just depends how old it is
It depends. A feeder goldfish lives to be about 2 years old. A fancy goldfish, (Black Moors, Fantails, etc...) can live to twenty years or more with proper care.
20 years
yes....
I don't now
160 - 25 = 135 135 + 135 = 170
Its in the nicktropolis map now