Virtual Aquarium

This is a quiet, calm fish tank for your screen. Fish of many colours swim back and forth, bubbles rise, and plants sway in the current. Click or tap the water to scatter food, and nearby fish will swim over to eat it. There is no sound, no score and nothing to win.

It works well full screen on a spare monitor, a TV or a tablet. If your device is set to reduce motion, the tank moves more slowly.

About once a minute, a less common animal drifts across the tank. A label tells you which one. You can also press Call a visitor.

• Moon jellyfish: a jellyfish has no brain, heart or bones, and its body is mostly water. It pulses its bell to move slowly through the sea.
• Seahorse: the male carries the eggs in a pouch on his belly and gives birth to the young. Seahorses swim upright and are slow swimmers.
• Manta ray: one of the largest rays, with a wingspan that can exceed seven metres in the biggest species. It filters tiny plankton from the water and glides by flapping its wide fins.
• Anglerfish: a deep-sea fish. The female of many species carries a glowing lure on a stalk above her mouth, which attracts prey in the dark. The light comes from bacteria living in the lure.

The drawings are simple illustrations, not scientific portraits.