If they're usually quite flirtatious in the tank, usually playing with /near each other and get along well, and you've seen the male frantically cleaning out his nest recently, then I'd say you're probably onto a winner.
Just before they "do their thing", you'll see him chasing her around the tank and being more playful than usual with her, especially close to the nest.
She lays the eggs, and HE will nurture them until they hatch, fanning them and making sure the temperature around them is ideal. The eggs are quite big and a yellowish colour....
Give it about a week - 10 days and you'll see the eggs start "swiming" with a tail. That's the babies living off the eggs for a few days (they look almost like tadpoles).