Are you comparing them to something like Chaeto? If so Chaeto might rank a 10 while a mangrove may rank a 2. They grow very slow compared to macroalgae. They are a tree after all. So unless you have hundreds in a huge mangrove fuge then they might not give you the results you are looking for. They are, however, a very unique and beautiful addition to a tank. I have several in my display.