I currently don’t have a frag tank, and other than my display all I have is a fish qt, which currently has another wrasse in it that will possibly see the shrimp as food.I put them in a frag tank or fuge until they have molted once. This gets them used to catching prepared foods (flake food usually for me), larger and fully prepared for captivity. I have not had great luck just throwing them into the display without doing this. I have a cuban hog in that tank that constantly thinks that it can get them, but they can keep away from him. I get them 20 at a time and they come in a bit smaller, but in a month or six weeks they usually molt and are an inch long, or so.