Tiny green anemones seem so innocent. I bought 3 or 4 just for their color, not knowing these were Anemonia Majanos, which quickly split and made more of themselves and spread. Soon I had 40 of these guys in my tank. They are attracted to light, and will climb the rockwork to get to the top. Their sting is damaging to corals, and eat up 'real estate' other corals could use. This is definitely a pest anemone, and using a syringe with boiling water, I removed every one of them.