In game I wouldn't even waste the mental cycles to think about his range...quick fold & move on but if I had to think about it, the abso worst hand I imagine he'd do this with is AK and even that's questionable. 66 is possible.

Pre I think we have to 3bet to iso the BU megafish.

I also wouldn't call this guy a "supernit". We don't have a strong enough read of supernit after only 60 hands, we only know that he's leaning towards being a tighter player.