Common name: Acorn Barnacles

The family Balanidae, commonly known as Acorn Barnacles, is a fascinating group of sessile crustaceans that are often found encrusting hard surfaces in marine environments. These barnacles are characterized by their conical, volcano-like shells made of calcareous plates, which protect their soft bodies inside. They are filter feeders, using their modified legs, called cirri, to sweep plankton and detritus from the water column into their mouths. This unique feeding mechanism makes them an interesting addition to marine aquariums, especially for aquarists interested in creating a biodiverse and ecologically functional tank.

Acorn Barnacles are often found in intertidal zones, where they endure fluctuating conditions of salinity, temperature, and water movement. This adaptability makes them hardy organisms, but they require specific care in aquariums. They thrive in tanks with strong water flow to mimic their natural habitat and ensure a steady supply of food particles. However, they are sensitive to poor water quality and require stable parameters, including salinity and pH, to thrive.

While not a common choice for reef tanks due to their sessile nature and specific feeding requirements, Acorn Barnacles can serve as natural filtration aids and add a unique aesthetic to live rock setups. They are compatible with most reef-safe tank inhabitants, as they pose no threat to fish, corals, or other invertebrates. However, their presence may attract grazing fish or invertebrates that could damage their shells, so careful selection of tank mates is essential.

Scientifically, Acorn Barnacles are intriguing due to their life cycle, which includes a free-swimming larval stage before settling permanently on a substrate. Their ability to adhere to surfaces with one of the strongest natural adhesives known to science has been a subject of extensive research. For aquarists, their presence can provide a glimpse into the complexity and resilience of marine life.