SPS Coral

SPS corals—small-polyped stony corals—are the showpiece corals of advanced reef tanks. Acropora, Montipora, Stylophora, and similar corals with tiny individual polyps create intricate branching or encrusting structures that grow slowly into spectacular formations. Colors range from pale pastels to vibrant blues, oranges, reds, and purples. Under strong light, many SPS corals display fluorescence and color depth that's breathtaking.

They appeal to experienced reef keepers who want the challenge of raising corals that require precise conditions and reward that precision with growth and color development. There's something deeply satisfying about watching an SPS colony grow from a small frag into a large, thriving coral. The achievement feels earned because maintaining the conditions these corals need is genuinely demanding.

They're advanced-level corals, and this is not a beginner-friendly category. SPS corals need intense lighting, stable calcium and alkalinity supplementation, strong water flow, and consistent parameters. A single swing in conditions can cause bleaching or death. Mistakes that soft corals tolerate will kill SPS. Understanding this reality is essential before investing in these corals.

The reward for meeting their demands is stunning growth and visual impact. An SPS-dominant reef is a display tank in the truest sense. The corals display incredible color variation, the colonies grow visibly over months and years, and the result is a thriving ecosystem that's genuinely beautiful. For experienced reefers willing to invest in equipment and monitoring, SPS corals justify the effort.

They don't tolerate casual care or approach-and-see attitudes. They require commitment to monitoring, supplementation, and consistent maintenance. But for someone ready for that commitment, SPS corals represent the pinnacle of reef keeping achievement.

SPS corals come from Indo-Pacific coral reefs, particularly areas with strong light and current. They inhabit shallow reef areas, reef crests, and slope areas where light is intense and water movement is constant. They're found from the Philippines to Australia to the Great Barrier Reef and throughout the Pacific. Their distribution is determined by light availability and water movement—they need both intensely.

In nature, SPS corals receive intense sunlight filtered through water. The light intensity drives photosynthesis in their zooxanthellae algae, which provide the energy source for coral growth and calcification. Different depths and light conditions select for different species—those in very shallow water receive intense light, those deeper receive less. The coral species available in the hobby come from various depths, but all demand significant light.

Water movement in their natural habitats is constant and strong. Reef crests experience wave action. Deeper reef slopes experience current from prevailing currents. This movement brings nutrients, brings oxygen, and brings food. It also stresses the corals physically—their branching structures are built to withstand that stress. In a stagnant tank, SPS gradually decline.

Water chemistry in natural reefs is incredibly stable. Calcium levels are consistently high. Alkalinity is buffered by rock and sand. pH is stable. Salinity is constant. These stable conditions exist because the reef is a buffering system—large water volume, massive rock structure, and biological cycling maintain parameters. In an aquarium, replicating that stability requires active management—supplementation, testing, and adjustment.

SPS corals grew in their reef environment through a combination of light, nutrient availability, water chemistry, and time. The growth is slow by terrestrial standards—fractions of an inch per year for many species. But over years, corals grow into impressive colonies. In an aquarium with appropriate conditions, that growth happens at the same rate as in the reef.

Most SPS corals in the hobby are collected as frags—small pieces broken from larger colonies and mounted on plugs or tiles. This propagation method is sustainable and actually beneficial to wild reefs, as it reduces pressure on wild populations. The frags are incredibly small and fragile initially, but given proper conditions, they grow into full-sized colonies. Watching a tiny frag grow into a large coral is part of the appeal for many reefers.

Tank size minimum is 75 gallons for a serious SPS setup. Larger tanks—125 gallons or more—provide better stability and room for multiple colonies. Larger water volume buffers parameters better and allows spatial separation of different SPS species to reduce chemical competition. Many serious SPS reefers prefer 150+ gallons for dedicated SPS displays.

Water parameters are critical and non-negotiable. Temperature 78-80°F, specific gravity 1.025-1.026, pH 8.1-8.4, alkalinity 8-10 dKH, calcium 420-460 ppm, magnesium 1200-1400 ppm. These parameters need consistency more than perfection—a stable alkalinity at 8.5 is better than one that swings between 8 and 9. Stability prevents the stress that causes bleaching and collapse.

Calculus testing and supplementation are ongoing requirements. Calcium and alkalinity decline as the corals calcify and build skeleton. Testing weekly or even more frequently guides supplementation. Two-part supplementation (calcium and alkalinity separately) or all-in-one products maintain levels. Without active supplementation, parameters drift downward and corals slow growth or decline.

Lighting is non-negotiable and expensive. SPS corals need 8-10+ watts per gallon of quality reef lighting. LED fixtures designed for reef tanks with appropriate spectrum (typically 6500-8000K for acclimated corals, higher blue spectrum for depth-simulated lighting) work well. The intensity matters—color and growth depend on adequate light. Underlit SPS corals lose coloration, grow slowly, and eventually decline.

Light positioning matters. Corals need light from above at reasonable intensity at their location in the tank. Shaded areas work for some species but not all. Experimenting with frag positioning to find optimal light for each coral species is part of successful SPS keeping. Some corals may need repositioning as they acclimate to the tank.

Water flow is essential. SPS corals don't just prefer flow—they require it. Strong return flow from the main system plus powerheads creating circulation patterns throughout the tank ensures adequate movement. Flow keeps waste from accumulating around corals, brings nutrients, brings oxygen, and supports the physical structure. Many SPS tanks run 15-20x turnover per hour from circulation—much stronger than soft coral tanks need.

Substrate is typically live sand with substantial live rock. The rock provides biological filtration and creates the reef structure corals attach to. 1.5-2 pounds of rock per gallon is common. The rock surface provides mounting points for frags. Many people use rock rubble or rubble-filled crevices as frag gardens where they mount new corals initially before moving them to display positions.

Filtration is important but works differently in SPS tanks than in fish-heavy setups. Mechanical filtration removes suspended waste. Biological filtration handles bioload. In SPS tanks, the corals themselves are the primary biological load—they consume nutrients but don't produce the waste that fish do. Proper skimming and filter maintenance prevent organic buildup that would trigger algae and nutrient spikes.

Protein skimming is highly recommended. A good skimmer removes organic compounds before they decay and create nutrient problems. In SPS tanks, skimming helps maintain water clarity and quality that supports coral health.

Automatic dosing systems are common in serious SPS setups. These systems automatically add calcium and alkalinity based on programmed schedules, reducing the management burden. While not essential, they help maintain the consistency that SPS corals demand.

SPS corals receive energy from two sources. First, zooxanthellae algae within their tissues photosynthesize under light, providing energy for growth and calcification. This is the primary nutrition source. Second, SPS corals are capable of capturing and feeding on very small organisms—bacteria, nano-plankton, organic particles—though this supplemental feeding is minor compared to photosynthesis.

Light is the primary food. Providing adequate light, properly colored and positioned, drives photosynthesis and supports coral energy. Zooxanthellae convert light into sugars that the coral uses to calcify and grow. Without adequate light, zooxanthellae starve, the coral loses energy, and growth stops or reverses.

Supplemental feeding with zooplankton cultures, phytoplankton, or specialized reef foods is optional but potentially beneficial, particularly for newly-fragged corals still recovering from the fragmentation process. Adding these foods provides supplemental nutrition and can accelerate growth and coloration development. Many experienced reefers add phytoplankton or zooplankton a few times weekly.

Carbon dosing—adding compounds that encourage bacterial processing of nutrients—is an advanced technique some SPS reefers use to optimize water chemistry while supporting nutrient availability for coral growth. This is optional and beyond basic SPS care, but it's a tool experienced reefers use. If you're unfamiliar with carbon dosing, focus on lighting, flow, and parameter stability first.

Trace element supplementation—adding iodine, iron, and other micronutrients—is sometimes used in dedicated SPS tanks to optimize coloration and growth. Specialty supplements designed for SPS are available. Whether supplementation is necessary depends on your specific setup and goals. Many tanks thrive without it. Others benefit from the additional nutrients. Experimentation guides decisions.

The simple version: strong light is the primary nutrition. Optional supplemental feeding and trace elements can accelerate results but aren't essential for survival. Many beginning SPS keepers focus on lighting, parameters, and flow first before adding supplemental feeding.

SPS corals don't display obvious behavior in the sense of movement or activity. Their polyps extend slightly to feed on plankton and photosynthesize, but the movement is minimal. What changes in SPS corals is coloration and growth. Under stable excellent conditions, colors intensify over weeks and months. Growth becomes visible—new branches extend, polyps multiply, the coral visibly expands. Under stress, coloration fades and growth stops. These changes reflect the coral's response to conditions, but they're slow changes.

Day-night cycling is relevant. Some SPS species show stronger coloration during daylight and fade at night. Some show different colors under intense light versus dimmer light. Observing these color changes is interesting and helps you understand how the coral is responding to its environment.

Compatibility with fish is good. Most reef fish leave SPS alone. Large aggressive fish might damage corals during movement, but peaceful reef fish coexist fine. The main compatibility consideration is fish that would eat small organisms that SPS corals feed on—but that's rarely a problem since SPS corals primarily feed on light anyway.

Compatibility with soft corals requires space and consideration. Some soft corals release chemical compounds that stress or kill nearby SPS. Others coexist peacefully. In general, separating soft and stony coral zones or spacing them widely reduces chemical competition. Many reefers choose to create SPS-dominant or soft-coral-dominant reefs rather than mixing.

Compatibility with other stony corals varies by species. Some SPS corals are more aggressive than others in chemical competition. Acropora species can be aggressive toward other acros and nearby corals. Montipora are generally less aggressive. Understanding your specific corals and spacing them appropriately prevents damage.

SPS frags should be secured to rock or tiles so they don't move around in current or tumble. Movement causes tissue damage and stress. Once established in a position, they should stay there unless being repositioned deliberately for light or growth management.

Fragmentation—breaking pieces from a healthy coral for propagation—happens naturally or intentionally. Many SPS reefers frag their own corals, either to propagate them or to manage size. Healthy corals regenerate the fragmented area and the frag grows into a new colony.

SPS corals live indefinitely in good conditions, like all corals. Given proper care, an SPS colony can live for decades. Growth is slow but continuous. A coral that's been growing for 10 years becomes large and impressive. Lifespan is essentially indefinite if conditions remain appropriate.

A healthy SPS coral displays vibrant coloration. Acropora blues, reds, and oranges are vivid and deep. Montipora colors are rich. The coral's polyps extend during the day, giving the colony a slightly fuzzy appearance. The coral grows—new branches extend, polyps multiply, the colony expands gradually. Visual health in SPS is obvious.

ColorBleaching—the loss of coloration and appearance of white or pale tissue—is the most common serious problem. Bleaching is usually stress-related, triggered by light shock, temperature swing, parameter crash, or physical damage. The coral has lost its zooxanthellae or the zooxanthellae have become dysfunctional. Early bleaching is sometimes reversible if conditions are corrected quickly. Extensive bleaching is usually fatal.

If an SPS coral bleaches, check water parameters immediately. If anything is off, correct it. Perform water changes. Reduce light intensity to half and gradually increase it back to normal over a week as the coral recovers—light shock sometimes triggers bleaching. If parameters are good and the bleaching was minor, the coral often recovers. If bleaching is extensive or parameters are poor, the coral will likely die.

Algae growth on corals can smother them or compete for space. Surface algae is minor and doesn't harm the coral. Heavy algae overgrowth is serious. Causes include high nutrient levels, inadequate flow, or excess lighting hours. If algae is a problem, address the underlying cause—test nutrients, increase flow, reduce light hours, improve skimming.

Physical damage from rough handling, fish, or tank manipulation shows as broken branches or exposed coral skeleton. Minor damage often heals. Extensive damage is serious and may kill the coral. Handle corals minimally and carefully.

Pests and parasites can afflict SPS corals. Common issues include flatworms, nudibranchs, and parasitic crustaceans that bore into skeleton. Identification and treatment require expertise. If you suspect pest problems, consult experienced SPS reefers or your aquarium shop for identification and treatment guidance.

Preventive care includes stable parameters tested frequently, adequate lighting and flow, careful handling, and regular observation. Quarantine new frags for 2-4 weeks in a separate system before introducing them to your display, preventing introduction of pests or diseases.

If your SPS coral shows signs of stress—bleaching, color loss, reduced polyp extension, slow growth—check parameters first and correct any issues. Observe lighting and flow. Make one change at a time and observe for a week before making additional adjustments. Corals respond slowly to correction, sometimes taking weeks to recover. Patience and consistency are key.