newbie to seahorse mating

I have six hippocampus erectus, 5 females, one male. Trust me, I do know the difference between male and female, and how he snuck in there I have no idea. I purposely wanted all females but now I am in for a whole new experience. My two large seahorses were seen doing the mating ritual dance at night, two nights in a row but never again. I was looking up at Maxine, today, who is the female Oliver seemed to be interested in and saw a white object slightly protrude from her opening and then a thin white milky substance was released. It was definitely not feces. What could this be and could the attraction be over for now?