Actually Vinh, just use that aquastick you got from me. Make a small ball of it, and stick toothpicks in it. The color shouldn't matter too much. I never bothered with this. But they will also hide in larger acro colonies as well.
They didn't pair them up for me. I was left to my own for that part. So I picked some YOUNG ones that looked like they had the right shape. Funny thing, I actually thought the male was a female, and the other way around for the female. Until the male stopped eating and I saw the babies it was carrying. Of course that was a while after I got them, as they were pretty young then.

Glad they worked out for you Vinh. And like I said, they would be worth it