They need the nest.
What happens is the male builds a nest and coaxes the female udner it. they embrace and she releases eggs which he then fertilises. they may repeat this a few times. He collects the eggs into the nest and chases the female away. From this point on the nest belongs soley to the male and the female plays no aprt in rearing the fry - she may even eat the eggs if she can (and any other fish in your tank certainly would love them). The eggs hacth quickly but the fry remain in the nest. Once free-swimming, the male no logner looks after them. Again, he may even eat them. While the male is still guarding his nest, however, he can get surprisingly aggressive towards all the other fish as he may consider them threats or intruders. Idealy, you need a seperate tank to breed and raise gouramies. Not only are the fry remarkably small and apparently very tasty, the male's aggression also makes it inconvenient and the fry, being as miniscule as they are, require tiny foods at first - infusoria and later baby brine shrimp or microworms - that they can't easily get in a community tank with strong currents and lots of larger hungry fish.