Ah, okay, so they aren't terribly fast growers. Good, more time for me to catch the remaining ones out of this rock! They're all little half-an-inch ones that can't hurt anything yet.
That's good to know, thanks. Any idea how much these lil guys move around, if food comes to them and they don't have to hunt it? I've been catching the ones on the rock when they come out to wander around, but I don't know if maybe they're doing that because they have to come out to get food, not because they need to wander for their health.