Soft Coral

Soft corals are corals that lack the rigid calcium carbonate skeleton found in stony corals. Instead, many species rely on flexible tissue and microscopic structural elements called sclerites for support. Soft corals are among the most adaptable and commonly kept corals in reef aquariums and are often recommended for newer hobbyists because many species tolerate changing conditions better than SPS corals.

Common soft coral groups include Zoantharia, Sarcophyton, Sinularia, Xenia, and Clavularia. These corals display a wide variety of growth forms ranging from encrusting mats and waving polyps to large leather-like colonies.

Most soft corals thrive in stable reef conditions with temperatures between 76–79°F, salinity around 1.025–1.026 specific gravity, and a pH between 8.0–8.4. Alkalinity is commonly maintained between 7.5–9 dKH, calcium around 380–450 ppm, and magnesium between 1250–1400 ppm. Unlike stony corals, soft corals do not heavily consume calcium and alkalinity for skeletal growth, but stable chemistry still supports overall health and long-term growth.

Soft corals generally tolerate and often benefit from slightly higher nutrient levels than many SPS corals. Nitrate levels around 5–20 ppm and phosphate levels between 0.03–0.15 ppm are commonly acceptable for many species. Systems that are excessively nutrient-poor can sometimes lead to poor growth, fading coloration, or reduced polyp extension in soft corals.

Most soft corals prefer moderate, indirect, and turbulent flow rather than harsh direct current. Proper flow helps keep detritus from settling on tissue while improving gas exchange and nutrient delivery. Healthy soft corals typically show steady polyp extension, gentle swaying, and consistent tissue inflation under appropriate flow conditions.

Excessive flow can cause polyps to remain retracted or tissue to appear stressed, while insufficient flow may allow debris and algae to accumulate on the coral. Leather corals such as Sarcophyton benefit from enough movement to help remove their periodic waxy coating, while species like Xenia often display stronger pulsing behavior in stable systems with moderate indirect flow.

Although many soft corals are considered beginner-friendly, some can spread aggressively or compete chemically with neighboring corals through allelopathy. Running activated carbon and maintaining regular water changes can help reduce chemical competition in mixed reef aquariums.