Wacthing a Spiny Soft-shell Turtle (Apalone spinifera spinifera in HD bury itself in the gravel and then stretching its neck extremely far to get some air all the while a Red Eared Slider is grooving to techo.
Softshells love sand. the rocks can damage their nails and shell if sharp enough. Plus sand is a lot lighter. They sell special sand at reptile pet shops. If you have any questions please let me know. I'll love to help I have a male softshell about the size of yours.