Tropical coral reefs are under serious threat, especially in the Caribbean, where hard coral cover has dropped sharply in recent decades. A major reason is the loss of natural grazers that keep algae and seaweed in check. One key grazer, the long-spined sea urchin (Diadema antillarum), has nearly disappeared due to two recent disease events. My PhD research focused on helping restore these urchins to boost reef health. I developed the first successful method to raise their larvae in the lab, tested what substrate the larvae prefer to settle on, grew juveniles for reef restocking, and used cryopreservation to save biological material for future efforts. These results make it possible to actively restore this vital species and support the recovery of Caribbean coral reefs.