Hard corals are generally broken down into two categories, large polyp stony (LPS) corals and small polyp stony (SPS) corals. The SPS corals have small polyps on a calcareous skeleton. SPS corals are usually either branching or plated. For the most part they enjoy bright light and strong currents. They are often fragile and are propagated by breaking off pieces. SPS hard corals are generally considered more difficult to keep than the LPS or soft corals and are not recommended for beginners.