Abdopus aculeatus is a small species of octopus in the order Octopoda. It has the common name algae octopus due to its typical resting camouflage, which resembles a gastropod shell overgrown with algae. It is small in size with a mantle around the size of a small orange (c. 7 cm or 3 inches) and arms 25 cm (10 inches) in length, and is adept at mimicking its surroundings.

World range and habitat Algae octopuses are found throughout intertidal zones along the Indonesian, Philippine, and Northern Australian coastlines. They primarily live in areas with abundant sea grass coverage and occupy dens built into the sandy seafloor, which they line with small pebbles. In its resting camouflage, A. aculeatus displays mottled ochre, gray, and brown colors that resemble a shell overgrown with algae, and dark arm bars reminiscent of hermit crab legs.

Feeding behavior Algae octopuses are most active during the day, leaving their dens to forage and returning at night. In some areas (mainly Northern Australia), Algae Octopuses will forage among coral, but typically they do not. They tend to feed on small crustaceans including portunid and calappid crabs by groping and pouncing on small rocks and clusters of algae, and digging into the sand.