Not for a long long time and maybe never. I only know 2 was to sex a melleri. You have to watch them pooping and see them flash the family jewels, or see a female lay eggs. I think I would notice the eggs.
I really don't care what sex mine is. He is a very loved little creature either way. He is named after the egyptian sun god so maybe he is a male. I do keep mostly males.
I just hope he decides to like me before his body is a foot long and that mouth will look like the grand canyon.