Common name: Giant Acorn Barnacles

The genus Megabalanus encompasses a group of large, strikingly colorful barnacles commonly referred to as Giant Acorn Barnacles. These sessile crustaceans are found in marine environments worldwide, often attaching themselves to hard substrates such as rocks, ship hulls, and even the shells of sea turtles and whales. Their robust, conical shells can range in hues of pink, red, and purple, making them a visually interesting addition to marine aquariums, particularly for aquarists interested in creating a naturalistic or biotope-style setup.

One of the most fascinating aspects of Megabalanus species is their filter-feeding behavior. They extend feathery appendages called cirri to capture plankton and organic particles from the water column. This makes them excellent natural cleaners, though they require a well-established aquarium with a steady supply of plankton or supplemental feeding to thrive. These barnacles are highly sensitive to water quality, and stable parameters with low levels of nitrates and phosphates are essential for their survival.

While they are not commonly kept in home aquariums due to their specialized care requirements, Megabalanus can be a unique addition to large, mature marine tanks or public displays. They are non-aggressive and pose no threat to other tank inhabitants, making them compatible with a wide range of peaceful marine species. However, their sessile nature means they cannot move to escape predators, so they should not be housed with species that may pick at or consume them, such as triggerfish or puffers.

Scientifically, Megabalanus is noteworthy for its role in studies of marine biofouling and intertidal ecology. Their ability to adhere strongly to surfaces has inspired research into bioadhesives and antifouling technologies. For aquarists, these barnacles offer a glimpse into the complexity of marine ecosystems and the fascinating adaptations of sessile organisms.