It will take a few weeks for it to fatten up (but not too much I hope).
The fact that is eating and moving around does point to a normal acclimation issue.
Carla and Mitch, you always have friends here, even if we can't offer a cup a of live sand to get you started.
I got lucky when I started my tank. Someone nearby bought the livestock including the sand from a soldier who was being deployed overseas. I got a couple of pounds of LS
filled with spaghetti worms and other life. I've passed on a cup to others in the area when asked.