Can you have two Diamond Watchman gobies?

[YellowThunder]

I see online that Diamond gobies can live in two but only if they are mated pair. Is there anyway to find this out and if I throw two in the tank that aren’t known as a mating pair what’s the chance they fight. Also it says they need live sand I don’t believe that to be true but just checking. Would be put in a 55 gallon with a small Sailfin Tang, a small red coris wrasse adult and also a pair of leopard wrasse.

 

[afrokobe]

I bought a pair when I had one, but I have no idea how to sex them. You would probably risk them fighting if they are the same gender.