BUT, depending on the species, different gouramies will show different breeding behaviours. Some ggouramies don't even build a bubblnest. Also, you may be mistaking aggression for breeding behaviour and there's also the possibility that you don't even have both sexes.
Can you tell us what species you have, how many, what sexes, what size tank, whether you have floating or tall-growing plants, the behaviour you are witnessing, what you feed your fish and whether you have a strong or weak current and the temperature of your water for starters? Also, knowing what other fish you have in with them and how many may be important as it might influence their behaviour and, also, your pH would be useful to know.