I have 2 males, both are around 20grams. They're both ornery but not towards each other and will "cuddle". To sex them all you do is look near the anal vent to see if there are 2 bumps or not. If there are (and it will be apparent that the animal has nads), you obviously have 2 males. I'd invest in a 10gal tank and go ahead and separate them. You never mentioned how old they both are. Eventually they'll want to fight around the sexual maturity age but to be 100% sure of a stress-free environment, just look into separating them. I use the 10gal fish tanks for mine with a mesh lid- they're very cheap.