Maryrox; getting your fry to lay eggs (breeding) is easy. It's raising the tiny fry .... well that's the challenge. Anyway, some males do not make nest before they spawn. Specially when there's water circulation. Look at how he swims when you put in a female. If he is sort of dancing, showing off his fins, that means he wants to spawn. If he is sort of holding his ground, saying I'm tough, he does not intend to spawn.
The same goes for the female, in a more submissive way. Dark colored females usually shows vertical markings on her body.
Males do need to "exercise" regularly, but I would not place a female/male in his sight for too long. He might become uninterested. Good breeders are usually aggressive.
The easiest way to determine males from females is to see the bottom of their bellies. Female usually has a white dot, males don't. Aggressiveness is not a sex factor. Both sex can and will become aggressive towards more quiet ones.
I hope this helps. Good luck on your breeding.