A calm aquarium, seen from the side — tetras schooling, an angelfish gliding, a bottom-feeder working the sand, plants swaying, bubbles rising, light rippling on the floor. When the room goes dark the tank follows: the light fades to blue moonlight and the fish settle low and slow. Every fish and every frame is computed in the browser; nothing is fetched and there is no sound.
Each school follows three plain rules — stay close, head the same way, don’t collide — in a 3D box, so a fish at the end of the tank arcs round through the depth of the glass instead of bouncing. Every fish, plant and coral is drawn from scratch in code. A seed pins the stocking and furniture so the same URL always begins the same way.
In the evening the light fades to moonlight, 19:30 to 20:30 by default and back up 06:30 to 07:30, and the fish go to bed one by one. At feeding time, 08:00 unless you say otherwise, flakes fall and everyone swims up to eat. Every few minutes a curious fish comes to the front glass and looks out.
No outbound request at all and no audio. The simulation is capped at 30 frames a second on purpose, and a small WebGL pass adds the light shafts and caustics; if WebGL is missing the tank simply shows without the light. It also builds as plain static files for any host.
Setup
A browser is genuinely enough — the Mac app and Fully Kiosk below are conveniences, not requirements.
F11 on Windows and Linux, ⌃⌘F on macOS.chrome --kiosk <url> — on macOS, open -a "Google Chrome" --args --kiosk <url>.Displays are ordinary web pages, so anything that can hold one open works: a Raspberry Pi on a monitor, a retired iPad, a Fire tablet, the browser built into a TV.
Configuration
Everything below, plus a live preview and a URL builder that writes the link for you, is at tank.livingkiosk.com/setup.
| Parameter | Default | Meaning |
|---|---|---|
tank | planted | reef for a bright marine tank. |
count | 1 | Fish density as a multiplier, 0.25–2. Schools never shrink below four; every species keeps at least one fish. |
night | auto | auto follows the clock; on is always night; off always day. |
feed | 08:00 | Daily feeding time, 24-hour, in the tank’s time zone, or off. |
bubbles | 1 | Bubbler strength, 0–2 or off. 0 is silent water. |
tz | the device’s | An IANA zone, for a screen whose clock is not the room’s. |
seed | — | Pins the stocking and furniture. Two screens without a seed will not be in step. |
dim | 0 | Black scrim over everything, 0 to 0.8 (fleet-wide convention). |
Tank is open source under the MIT licence. Run it yourself with one command. The source opens to the public soon.