Photo albums!!!
A male and a female of the species.
Ok, no community big boys. Community tanks with dwarfs and pygmies are more and more popular, though. Especially new enthusiasts start with small tanks.
Edit:
I was checking DD's pin on the small cichlids again. It wouldn't take much to add the cockatoos, who are becoming popular, to the thread more thoroughly. And it is possible to sex the young ones. An addition of pictures of a male and female of each species would be great too.
(Actually I get it mixed up in my head that I'm working a plan to mix pygmy gourami and cockatoos in a community tank and the knowledge problems that creates. So excuse me for asking for what you are already making great strides in achieving.)