Center for Marine Biodiversity and Conservation

Coral restoration efforts are increasingly bottlenecked not by biology but by the manual labor required to maintain nursery tanks, particularly the routine scrubbing of algal fouling from coral growth substrates. This capstone project, "Foul Play," addresses that bottleneck by pairing Coral Guard, a nontoxic algae-deterrent tile coating developed at the Scripps CRE Lab, with a custom-built single-axis robotic gantry system ("Sisi") capable of dislodging fouling using water pressure alone. The system was designed and fabricated from first principles over approximately 10 weeks, integrating NEMA 17 stepper motors and TR8×4 lead screws on a V-slot aluminum frame, GRBL-based motor control via an Arduino Uno and CNC Shield, MOSFET-switched pump control, and a Flask web application supporting mouse, keyboard, and voice-driven operation. A factorial experiment varying nozzle standoff distance and sweep duration identified an optimal cleaning configuration (1-inch distance, 10-second sweep), which was evaluated using a companion image-analysis tool, the Coral Guard Tile Scorer, that quantifies algal fouling coverage from RAW tile photographs using CIELAB color space segmentation and deep-learning-based coral masking. Results showed cleaning effectiveness comparable to manual toothbrush scrubbing, with no visible coral tissue damage, while reducing required human presence by an estimated 10–15x and projecting roughly 33 hours of annual labor savings per 10 nursery tanks. These findings demonstrate that automated, contact-free cleaning is a viable path toward scaling ex situ coral restoration operations.