Difference between male and female gourami's

Depending on which gouramis you are talking about, it's actually pretty easy to tell the males apart from the females when they are sexually mature.

For the Trichogaster species like blue, pearl, 3-spot, cosby, etc, the male will have an elongated pointed dorsal fin. Female's dorsal fin will be short and round. Females will usually have a fuller, rounder abdomen too (sorta like your avatar pic..congrats, by the way if that's you ). Males and female Trichogaster will usually have the same amount of colouring, so determining the sex requires a more careful eye.

For the Colisa species like dwarf, neon red, flame, sunset -- these fish tend to be more sexually dimorphic, meaning there are decernable differences in colouration between the sexes. Males are usually very colourful, while the females tend to be less so.

If you put the Trichogaster and Colisa species together, they won't breed.