Ultra Aquarium is a living 3D reef for Windows 10 and 11 (64-bit), usable as a screensaver or live wallpaper. On multi-monitor setups it spans every screen as one tank, with a bezel correction setting, and you can choose which monitors show the reef. Press F to feed the fish. An octopus lives in a cave and changes color to blend in, and a blue-spotted stingray swims through. Quality 1 runs on laptop graphics, and quality 10 is meant for a dedicated graphics card.
It is free with no ads, and the installer is about 17 MB. The page says a donate button or bonus content might come later, and that it was built with a lot of AI help. It also has an optional webcam head-tracking mode that the page says is processed locally.
I wanted a calm, good-looking reef screensaver that actually spans a multi-monitor setup as one tank instead of repeating per screen, and couldn't find a free one without ads, so I built it.