Caulerpa filiformis is a green marine plant that belongs to the family Caulerpaceae. Species in the Caulerpaceae family grows from a horizontal stolon and are able to spread quickly over large areas of substrate. Caulerpa species can often become the most dominant plant species on reef and sandy areas in the waters of southern Australia.
Caulerpa filiformis is found on exposed rocky reefs in central New South Wales from Sydney to Port Stephens. It is also known to occur in South Africa. It can be found on rocky reef in shallow waters (from 0 – 6 metres) and is often exposed on a low tide. This species was first recorded in Australia in 1923 and was possibly introduced from South Africa via a ships hull or ballast. This species is prolific on many rocky reefs and is the most dominant marine plant displacing many other species. The rocky reefs around Port Stephens are dominated by Caulerpa filiformis that covers huge amounts or rocky reef.
The maximum thallus height of Caulerpa filiformis is approximately 18 cm.