Fish Tank Plus

Fish Tank Plus is a living 3D reef you can keep open in a browser tab, on a laptop, a Chromebook, a phone or a tablet. There's nothing to install and nothing to sign up for. Rays glide past, wrasses run a cleaning station, the coral glows when the lights go down, and Octopus Boy lives in a little cave, crawls across the sand and changes colour as he goes. You feed the fish, play with the fish count, swim speed and lighting, and earn fish sticks to unlock new things, so the tank slowly turns into your own. It's become a popular one to leave running in the background while you work.

If you're on Windows there's also a desktop version that works as a real Windows screensaver, spans several monitors as one big tank and has much heavier AAA-style graphics, including a new scene where the reef is a ring of sea on a station orbiting the Moon. It's free on the Microsoft Store: https://apps.microsoft.com/detail/xp8c5d95n4q26p

It's free with no ads. I'm a solo dev and built it with a lot of help from Claude, ChatGPT and Grok.