ZOO MED DR.TURTLE SLOW RELEASE CALCIUM BLOCK Dr. Turtle® is a slow-release calcium block that conditions water while providing a calcium supplement to promote healthy shell growth for aquatic turtles. To use, simply place the Dr. Turtle® Block in your turtles water supply Turtles require UVB lighting and heat for proper shell growth and development. Provide your turtles with 5.0 or 10.0 UVB lamps For optimum health.