I've read that clownfish are born kinda neutral, then develop based on their environment. They start as males, then can change to females - the largest one usually becomes the female. If you're trying to pair them, it's best to get them when they're tiny, before they've changed sexes.
I've found that breeding clownfish isn't too hard, but raising the babies is a challenge. I came across a guy who's had success with this - he's got a system down for growing Nexarios and hatching brine shrimp to feed them. His clowns apparently spawn every week. He removes the eggs from the tank and puts them in a separate setup. Just a heads up, this is a really time-consuming process.
They seem to prefer breeding on flat surfaces. This guy noticed his clowns kept laying eggs in one spot, so he put a tile there for them to use. When they'd laid eggs, he'd remove the tile and take care of the eggs separately. Sometimes he'd wait until they hatched, then scoop up the babies at night when they'd swim to the surface. His clowns are Black Ocellaris, btw - I've got a link to some info on breeding them if you're interested.
Who Gives A Fish Forums
⇧
⇩