SPS Corals

SPS stands for Small Polyp Stony, a group of corals characterized by small individual polyps and hard calcium carbonate skeletons. SPS corals are among the most recognizable and popular corals in reef aquariums due to their incredible colors, intricate growth patterns, and reef-building capabilities.

In nature, SPS corals are responsible for forming much of the structure that makes up coral reefs. By continuously depositing calcium carbonate skeletons over generations, these corals help create the framework that supports entire reef ecosystems.

For many hobbyists, SPS corals represent the pinnacle of reef keeping because they often require stable conditions and reward good husbandry with exceptional growth and coloration.

Why Are SPS Corals Important?

SPS corals play a major role in both natural reefs and reef aquariums.

They contribute to:

• Reef building
• Biodiversity
• Habitat creation
• Coral growth and propagation
• Visual appeal within reef aquariums

Many of the most iconic reef aquarium corals belong to the SPS category.

What Makes SPS Corals Different?

The defining characteristic of SPS corals is their small polyps and rigid skeletons.

Unlike many fleshy corals, SPS corals typically have:

• Small feeding polyps
• Dense skeletal structures
• Branching, plating, or encrusting growth forms
• High growth potential
• Strong dependence on stable water chemistry

Although their polyps are small, SPS corals are still active animals that feed, grow, and respond to their environment.

Common Types of SPS Corals

Popular SPS corals include:

• Acropora
• Montipora
• Pocillopora
• Stylophora
• Seriatopora
• Birdsnest corals

Each species displays unique growth patterns, coloration, and care requirements.

How Do SPS Corals Obtain Nutrition?

Like many reef-building corals, SPS corals rely on multiple nutritional pathways.

Photosynthesis

SPS corals contain zooxanthellae that provide energy through photosynthesis.

Heterotrophic Feeding

They also capture food from the water column, including:

• Zooplankton
• Phytoplankton
• Marine snow
• Dissolved organics
• Prepared coral foods

Although photosynthesis supplies much of their energy, feeding can provide important nutrients that support growth, coloration, and tissue health.

SPS Corals and Coral Nutrition

One of the biggest misconceptions in reef keeping is that SPS corals survive entirely on light.

While lighting is extremely important, SPS corals still require nutrients to support:

• Tissue growth
• Metabolism
• Coloration
• Reproduction
• Stress recovery

Nutrients such as:

• Amino acids
• Proteins
• Fatty acids
• Vitamins
• Trace elements

all contribute to the overall health of SPS corals.

Successful SPS systems often combine strong lighting with consistent nutritional support.

SPS Corals and Water Chemistry

Because SPS corals build substantial calcium carbonate skeletons, they consume significant amounts of:

• Calcium
• Alkalinity
• Magnesium

As colonies grow, demand for these elements increases.

For this reason, stable water chemistry is often considered one of the most important aspects of SPS coral care.

Rapid fluctuations in major parameters can negatively affect growth and overall coral health.

Common Misconception: SPS Corals Need Ultra-Low Nutrients

For many years, SPS reef keeping focused heavily on maintaining extremely low nutrient levels.

Modern reef keeping has shown that SPS corals often benefit from balanced nutrient availability rather than nutrient starvation.

Appropriate levels of nitrate and phosphate can help support:

• Growth
• Coloration
• Tissue health
• Biological stability

The goal is nutrient balance, not nutrient elimination.

SPS Corals and Coloration

SPS corals are famous for their coloration.

Color development is influenced by:

• Genetics
• Lighting
• Nutrition
• Water chemistry
• Stability

The most vibrant SPS corals are typically found in systems where all of these factors work together.

There is rarely a single factor responsible for exceptional color.

The Bottom Line

SPS corals are Small Polyp Stony corals known for their hard skeletons, vibrant colors, and reef-building capabilities. While they rely heavily on photosynthesis, SPS corals also benefit from proper nutrition, stable water chemistry, and balanced nutrient levels. Understanding the relationship between lighting, feeding, and stability helps reef keepers create conditions that support healthy growth, exceptional coloration, and long-term success with SPS corals.