Im not a fish biologist or a pro but. When in spawn the males stay on the nest to fan and protect. Not sure but usually no deeper than 24" of water so u can see them when the water is clear. I know everyone probably knows this.

I had a LMB as a pet that i got off of the stock truck. I did this to observe the behavior of "him". I know his sex because at about 13" he started making a nest in the bottom of the aquarium and became very agressive even towards me, when I cleaned the tank.