Can Tropical Fish Change Gender?

Can tropical fish change gender?
Thanks to @Sue  for this answer!

No. This misconception arises because all fry look female. At puberty, male fish begin to change appearance. Late developing males retain their female appearance for a longer than usual time, and the owner is convinced that the fish is a female which has turned into a male. This delayed puberty is well known with swordtails.

There are some species of fish where subordinate males take on female appearance to avoid being bullied by the dominant male. These so-called sleeper fish may look female but they are male, and never take on full female colouring. If the dominant male should die, one of the subordinate males changes to typical male appearance. An  example of this is cockatoo cichlids, Apistogramma cacatuoides.