sand generally isn't the best substrate for a turtle tank unless it is a desert tortoise you're taking care of. when turtles eat, they aren't very careful about what they are chomping on, so if your turtle eats something that has sand on it, the sand can damage its mouth and its whole digestive tract. furthermore, the sand can get into the turtle's armpits and around its soft skin, causing painful sores. i would suggest wood chips, coconut fibers, or some other type of soft fibers for reptile tanks. as for the rocks, as long as the rocks have no sharp edges and aren't crowding the turtle's walking space, they should be ok to put in the tank.