my male was very shy and my female was very active until they reached maturity. Now they are both very active. I thought it was interesting to see the male go from mister scaredy cat (or scaredy ray in this case) to the man of the tank. It was cute.
The more you're in front of the tank watching them, feeding them, wiggling your fingers at them, the more social they'll be.
I got mine last wednesday and my female is already climbing the side of the tank begging for food. Male is still shy, but he's starting to come around.