An electric green open brain (Trachyphyllia geoffroyi, I believe) taken under actinics. The tentacles are the color of egg whites under metal halides, but reflect the purple-blue of the actinics making a spectacular contrast. These brains aren't particularly aggressive - this one touches open green star polyps during the day and doesn't sting them. It's the brightest colored coral in my tank. It opens to about 4 times the size of the skeleton while the metal halides are on, but shrinks down to about half that size 5 minutes after the metal halides turn off.
