Your three interventions
Tap open water to drop food. Drag one creature directly onto another to hatch a mixed descendant. Drag any creature outside the glass to remove it. Tap a creature without moving it to inspect its species.
What happens by itself
Creatures seek food, flee or hunt, form shoals, age and reproduce. Traits cross and mutate. A divergent lineage becomes a new named species; every lineage can flourish or disappear.
When intelligence takes hold
Social, intelligent species may found reef cultures. They choose what survival demands: algae gardens, hatcheries, filters, healing pools, current turbines, defensive reefs, light collectors, memory archives, seed vaults, shoal beacons, shelters or hunting lures. Each structure changes the simulation around it.
Time controls and autosave sit outside the ecosystem. The aquarium pauses when its tab is hidden and restores from this device automatically.