They go into a "down mode" so to speak. It is basically them sleeping, but they are at a minor attention. They will still be reactive, but it will take some time for them to completely perk up. This is one of the reasons why you don't turn on every light in the morning when the fish were used to dark. Sends them into shock.
Some fish lightly swim, some float, some sink, I think that depends on the individual or the species when they "sleep". I've noticed more bettas chill at the bottom, my rainbows and danios lightly swim, my flowerhorn will sometimes full-on lay on his side on the bottom, my bichir will float, and other fish will do either.
And he should be doing that. Those are his women and I'm sure he is not going to give them up. Normal dominant male behavior, at least for other fish. I have no guppy experience, so I'm just projecting from other fish experience.