Welcome Iragil. Great to see someone all the way in China joining here. Nice frogs, and as far as the pixie being a boy, it's a little too young (baby-juvenile). If I had to judge given a few top shots of your pixie, it looks like he is developing a broad head, so if I had to guess; I would say male. Feed him plenty while he is growing -- have you checked out the care sheet for pixies?

This from what I've seen, is the biggest frog forum. Even if it had a little less memers on here compared to another site I'm thinking of, it is still the most developed and excellent staff here. Feel free to ask more questions.