Yes, some fish even have standards. In Bettas, Males are deemed attractive by how well built their bubble nest is. Yet in live bearer society, males chase females either until the female wants to mate, or until the female gets tired, than mate with them.
Some can be like betta males have longer fins then females. Or you can see a webites that have photos of the fish you will like too see the difference of the female or male. You can google (or others like yahoo) and type down the fish name with gender ( also make sure you write down photos or picture in it) then you can see difference.
a pet store
In many fish species, including bettas, males typically have longer fins, brighter colors, and a slimmer body compared to females.
Female guppies are larger and plainer. The male is distinctive for his long, flowing, colourful tail and generally brilliant colours.
A guppy fish is a live bearing fish, but the female generally does not take care of her young, and will eat them.
All clown fish are born male. When the female of the group of clown fish dies, the most dominant of them will turn female.
Male floran fish will have a hump head where female does not. however it need to be looked closly if the fish were very young or not yet grown well.
they love one another the females are more com then male fish
Because she's probably hiding!!
The "attractive" skin that is left on the fish.
Here are two that I was able to find. on the left is a reagular (female silver molly) on the right is a (fancy tail lyretail female sailfin molly)
it depends on the type of fish, you can generally find a special food made for your type of fish at the petstore.