I found these great calcium treats at Petsmart last year and my crabs loved them and yes I love the fact that they produce hot pink and sky blue crab poos. I tossed one in the tank yesterday. This morning it was yet untouched but tonight… HOUSTON WE HAVE POO!! You can see the pooper in the corner of the pic. Obviously some of the stuff is shavings but its quite obvious which is the poo. Their food passes through their bodies rather rapidly and they obviously clean their shells out as they poo. I purposely placed the treat up in the turtle dock so I would be able to gauge when it was first touched.
To give you an idea of what this started out as: