Cichlids

I am an experienced aquarium owner. I have a 90 gallon tank and 5 cichlids that have been in the tank for at least 8 years. They have thrived in the tank until now. We got them as babies and they have grown up together.

We are wondering why they chase each other around and around in circles. And in the last day or two we have noticed that they have started going nose to nose as though they are challenging each other. Why are they doing this and is there anything that we can do?

Thanks for any advice.

Thanks for your idea. We had also thought that it was a territorial thing. So we will try to add some more places to hide. We had taken some stuff out and think that maybe they need more as they had before. They are yellow rams. But we don't know the sexes. Is there a way to determine sex of the fish.