Take the Digital Plunge and Make an ASCII Aquarium

Taking care of pets is a lot of work, especially for those with a busy schedule. To avoid the constant babysitting a dog needs, many people who want a companion will opt for a fish tank. This seems to be the perfect compromise on paper — fish may not be the best companions, but they are fun to watch and you don’t have to get up early in the morning to take them for a walk.

However, in reality, maintaining an aquarium does take a lot of work. There is still a lot of cleaning, measuring, adjusting, and feeding to be done, or the fish aren’t going to be very happy. And then there are arrangements for vacations — unless someone stops by to help out, the fish might all be floating belly-up before it’s over.

Kert Gartner is someone who really wanted an aquarium, but in terms of maintenance, a pet rock was more his speed. So, rather than taking the plunge, he came up with a solution that better suited his tastes: he built a digital aquarium. No, this isn’t some lame fish screensaver. Gartner created a tiny animated ASCII fish tank that runs on a Cheap Yellow Display (CYD). It is every bit as interesting as a real fish tank (in its own way), and it requires zero maintenance.

The project, called ASCII Aquarium, runs on the ESP32-2432S028R CYD, a tiny touchscreen development board with a built-in 320x240 display. Rather than simply looping a prerecorded animation, the aquarium is rendered live by the ESP32 microcontroller. Fish wander around the screen, avoid bumping into one another, school together, and chase floating food flakes that appear whenever the user taps the display.

The fish and other sea creatures are made entirely from ASCII punctuation and characters. Bubbles rise continuously through the tank while animated seaweed sways at adjustable speeds. Users can customize nearly every aspect of the display, including fish population, bubble count, seaweed length, visitor frequency, and background themes.

Special guest creatures occasionally drift through the tank as well. Seahorses and octopuses appear at configurable intervals ranging from once an hour to dozens of visits per hour. For more options, there is a hidden HUD menu tucked into the corner of the touchscreen that unlocks additional controls, creature tests, screenshot capture tools, and randomization functions.

The aquarium also doubles as a clock. Users can enable internet-synchronized time updates over Wi-Fi, choose between 12-hour or 24-hour formats, and select from several clock layouts and colors. A built-in Wi-Fi panel allows the device to scan for networks, save credentials, and synchronize time through NTP servers.

For a more realistic experience, users can add an optional 50 mm beam splitter cube. When positioned correctly above the screen, the optical cube reflects the aquarium in a way that makes the fish appear to float inside a small glass block. The effect transforms the already charming desktop gadget into a tiny holographic art piece.

Perhaps the best part is that, unlike a real aquarium, this one never needs cleaning, filtering, or emergency vacation planning. The fish never die, the water never turns green, and there is absolutely no risk of discovering snails taking over the tank overnight.