When they mate, the male will disappear into his hidey hole and not come out for about a week. He stays in there fanning the eggs with his tail and keeping the fry safe until they have consumed their yolk sac and are ready to venture out. Though I have to admit that by the time my male got to his seventh batch in 6 months, he was getting a bit blase and started sneaking out for quick breathing spells.
BN's are cave spawners... the male will trap an egg laden female in the cave, a and they will do their thing.
If they are just out and about then it liekly to be aggression... when they are breeding you will find they normally ignore each other until spawn time...
What do they look like? Do they both have a bristly nose?
If so they are both male and it will be fighting...