Thank you, very much, Diamondbacks4Life. Yes, it really looks like dominance dance, because Earl believes aquaterrarium his seniority

I was not sure, but exactly it looks like dominance dance.
And about the finger nails... I don`t know, may be it is wise to wait a bit else. Earl is too little else for exactly determination of sex, I think. And the turtle exactly responds to name Shipa

not Earl or Graf. Suddenly, I called him(her) for hissing (hissing in Russian is шипение [ship-enie]) as Shipa (sounds like word ship in English)

Turtle hears this sound better, perhaps. Exactly that both know their names. I have heard that in China red ear sliders can participate in easy street show with lucky tiсkets.