Reviving Old Hardware: Maker Turns Cheap ESP32 Yellow Display Into a Feature-Rich Miniature Digital Aquarium

For many technology enthusiasts and hobbyists, the parts box is a double-edged sword. On one hand, it represents a treasure trove of past inspiration, experimental prototypes, and leftover components; on the other hand, it is often a dusty graveyard for hardware that once held immense promise before being sidelined by newer projects. Yet, the DIY electronics and maker community has long thrived on the art of resurrection, continuously finding creative ways to repurpose dormant silicon. The latest example of this ingenuity transforms a popular, ultra-low-cost microcontroller display into a fully interactive miniature digital ecosystem, complete with nearly one hundred species of marine life and zero maintenance required.

The project, which has quickly captured the attention of the maker community, was conceived by a developer and hardware hobbyist known online as PowerfulChart560. Sharing their creation on the vibrant ESP32 community forum on Reddit, the developer introduced what they have dubbed the ESP32 CYD Aquarium. Designed specifically for the ubiquitous and remarkably inexpensive ESP32 Cheap Yellow Display—widely referred to in the community simply as the CYD—the project converts the compact hardware module into a lively, pocket-sized simulation of aquatic life, serving as an engaging desk toy or decorative set piece that doubles as a functional clock.

The underlying hardware driving the project is notable primarily for its accessibility. The ESP32 CYD module has become a staple among microcontroller hobbyists due to its combination of integrated Wi-Fi and Bluetooth capabilities, a bright color touchscreen, and an exceptionally low price point, often hovering around the five-dollar mark. Despite being designed as a versatile development board for IoT projects, home automation dashboards, and custom sensor monitors, these units frequently end up sitting idle once an initial experiment concludes. By channeling this unused hardware into a polished graphical simulation, the new project offers a compelling alternative to letting the silicon collect dust.

Upon booting up, the ESP32 CYD Aquarium launches directly into a dynamic, animated underwater simulation. The virtual tank is populated by a diverse roster of approximately one hundred different species, meticulously organized within a dedicated catalog file known in the source code as SpeciesCatalog.h. To mimic a living, breathing ecosystem, the simulation incorporates weighted spawn rates, distinct family silhouettes, and six separate size classes for the virtual fauna. Users can watch everything from small reef fish darting across the screen to much larger marine animals gliding past, including sharks, whale sharks, and reef mantas, all rendered smoothly on the compact display.

Beyond serving as a passive visual display, the project introduces a degree of interactivity that elevates it beyond a simple screensaver. The software features an in-tank reef guide that is both fully paged and touch-sensitive. As users interact with the simulation, the system tracks and records which species have been discovered, storing this progress data locally within the device’s file system using LittleFS under a designated field guide JSON file. This gamified discovery element encourages users to keep the display running as they try to log every single creature included in the simulation’s extensive marine catalog.

Furthermore, the simulation includes an integrated tank camera feature that gives users a closer look at the virtual wildlife. By tapping on any individual creature swimming across the screen, the display shifts focus to follow and zoom in on that specific animal. A subsequent tap allows the user to easily zoom out and return to the wide-angle view of the entire tank. Combined with an embedded 12-hour clock function, these features transform the humble development board into a functional, aesthetically pleasing desk accessory that requires none of the feeding, water changes, or filtration systems associated with real-world fishkeeping.

For hobbyists interested in exploring the project and giving their own unused development boards a second lease on life, the complete source code and installation resources have been made publicly available. Francis Tse, who maintains the project repository, hosts the open-source files on GitHub under the project title esp32-cyd-aquarium, allowing anyone with a compatible yellow display and basic flashing tools to deploy the digital ecosystem onto their hardware.