that is NOT a mating dance....
I have a 24" silver right now as well. 6 months back, I picked up a 20" silver. I had two 20" silvers at the time. For the first two days they were fine, then one night I walked in and they were swimming around each other in a circle. Exactly how a Tornado would spin. They would do this for 5 minutes on end, then stop for a while and do it again. Both aro's were exactly the same size, but looked nothing alike. My one has a skinnier body, but the bottom jaw goes past his upper jaw about a 1/4" or so (a lower over bite). The other guy's jaw's were the same size but his head was HUGE and the rest of his body was much bulkier. I ended up only having the big headed one for a few days, because the circle thing was freaking me out and they ended up starting aggression but still to this day I dont know the difference between a male and female.
what your describing my aro does every water change as well. Aro's need to keep moving. All he is doing is moving, and waiting it out until your done cleaning the tank. I also grew mine from 3".
I also have one in a small grow out tank that is 3" that I grew from the yolk...