Can ou post pics? pebbles explained it all quite well but there's even mroe you can look for. besides having a longer dorsal, extended finr ays on their dorsal and anal fin and more red-orange coloring on the throat/underside area, males also have a more pointed dorsal fin (though the extensions sometimes mask this) and look more stream-lined over all. They are also larger at maturity and tend to be darker and brighter-colored than the females which usualy have some grey-green highlights but only limmited amounts of orange. When viewed from above, females are very obviously wider (when ready to spawn) and generaly look deeper-bodied and more rounded when compared to a male. If you have 2 of different sexes, you should be able to see a very obvious difference between the two. If they look very similar to you, they must be the same sex (unless they are still much too young).