Yeah, having watched them for a while I can say it's going to be the large male, the smaller male is hiding away in another corner, the male keeps offering himself up against the coconut I think it will be a tight squeeze lol. I Will shortly do a 30-40L w/c.
In other news one of my Algae/Amano Shrimps in my 17L is carrying a mass of eggs under her body, I don't think the babies survive unless they are in brackish water though?