I've been calling it "Dancing Naked" lol. Then I noticed he does it a lot more lately and started to worry. I'm brand new to Frontosa behavior. He loses all color then tucks himself in a dark corner and gently spins himself around. Couldn't tell if he was happy or stressed.
A bit odd for a single individual, the circle dance is typically what a pair does when spawning, often (but not always) in a protected spot if such a spot is available.
Had a couple of oddballs in the tank at the time, a female leftover from my old Burundi group (until I traded her not long after), and a couple of rotkeil severums-- I'd been breeding/raising the rotkeils, had loads of them and had them everywhere at the time.