In fact, they were having an argument when I fed them this morning. Their colors deepen when they are having a disagreement or they are protecting their eggs or babies. The silver fish, the male, gets very, very black stripes when he is upset.
The female is the blue marble and because she is higher in the water, it means she most likely has the upper hand (or fin).
In the video below, you'll see how they waggle their fins at each other. They also resort to pushing. But angels - even male, alpha angels - rarely hurt each other or do any real harm. Unfortunately, I had to take this video from a distance because once I get closer to the tanks, they stop to look at me!
You can also see the top of the tank below them. That is where Lindsay and Stevie are caring for their young. I keep the top partially open because I am constantly pouring baby brine shrimp into their tank for the young to feed on.