So it's hard to tell from your picture. Females are much bigger than males. Males will use their front fins to kind of like do push-ups in the sand they will hold the front part of their body over the substrate where females usually lay flat on the substrate. Hope this helps.
Also they are diggers and sifters so sand is a better alternative as a substrate for them. The rocks you have in the tank right now can damage their barbels in the front. Also because they're scaleless it can also damage their bodies in the long run.