sexing of freshwater fish

Question
can u tell me how i can know the difference between a male and female in any goldfish, catfish, blue ram, gouramis,tetras,barbs sharks & angles

Answer
hi and thanks for the question.  sexual differences vary by fish species.  for example most chiclid(such as the rams)it is impossible to tell except during mating.  the male ram becomes more vividly colored. as for the gouramis, tetras, and sharks well the only way is unfortunately to cut them open and look inside.  please note that most sharks have never been bred in captivity for this reason.  a lot of tetras are like this as well.  as for goldfish, the male has an appendage(kind of like a penis) between his bottom fins. it is more noticeable at breeding time.  though good luck on breeding goldfish as it takes exact pH and water temperature.  the angles are a trick as they are chiclids too. surprise, not really since discus are also chiclid (members of the chiclidae family).  You probably already know what that means--sexual differences are nil at best.  the convicts(another chilid) is one of the few chiclids with obvious sexual differences----the female has a bright orange spot on her which is absent in all males.  as for catfish there are none and to the best of my record they have never bred in captivity.  only recently a related fish, the pleco, has breed in captivity.  sexual differences are unknown on the plecos but it does require a mud bottom pond of at least 2000 gallons, with mud and rock caves and very high pH.  if breeding is your fancy your best luck would be either guppies or members of the Poecilia family (mollys, platys, and swordtails) as they all have the appendage and breed readily in captivity.  many arrive in pet stores pregnant.  the male swordtail has the sword, the female doesn't.  i hope my advice helps, let me know.

good luck

timm