The Black Cucumber, Holothuria atra, also known as the Black Sea Cucumber, features a black/brown body that can grow up to 3-4 inches. They are reef safe but can emit poisonous toxins if attacked and injured. They will spend much of their time buried in sandy substrate - therefore a sandy bottom is essential. They will feed mostly on algae and detritus through sifting the sand. As they are easy to care for they make an excellent beginner cucumber species.