Caulerpa is a fast growing macro algae. It is a green algae which sends out runners and will grow leaf like structures that will look more like features. The ‘leaves’ can grow as large as 4 inches long and ¾ of a inch wide. You find it to be very nice looking macro algae. But don’t be fooled by its looks. It can quickly spread across your rock and substrate, even chocking out corals or other forms of algae making it a rather invasive macro algae for a display tank depending on your cleanup crew and fish. Caulerpa is a great algae to grow in a sump or refugium for nutrient removal as it will quickly remove nitrates and phosphates from the water out competing many other forms of algae for these same nutrients.