SPS corals: starter species and difficulty tiers
The SPS (small polyp stony) coral is the apex of the reef-keeping hobby, and the SPS coral is also the most demanding of the commonly kept corals. The SPS coral is the coral that requires the most stable water parameters, the most intense lighting, the most consistent flow, and the most vigilant husbandry. The SPS coral is the coral that rewards the experienced reef keeper with the fastest growth, the most intense coloration, and the most impressive display. The SPS coral is also the coral that punishes the inexperienced or inattentive keeper with the fastest decline, the most dramatic tissue loss, and the most discouraging "SPS melt" that is the rite of passage for many new SPS keepers.
This article is going to walk you through the difficulty tiers of the SPS corals — the species that are forgiving for the new SPS keeper (the "starter" species), the species that are intermediate (the "growing" species), the species that are advanced (the "expert" species), and the four mistakes that turn a stable SPS tank into a crash. I am a reef hobbyist with 15+ years of experience ranging from nano-reefs to 300-gallon mixed reef systems, and the SPS corals are the corals that have taught me the most about reef chemistry, reef husbandry, and reef patience. The SPS coral is the coral that demands the most, and the SPS coral is the coral that gives the most in return.
I want to be clear at the start: the SPS coral is not for the new reef keeper. The new reef keeper should establish the tank with soft corals and LPS (large polyp stony) corals first, and the new reef keeper should add the SPS corals only after the tank has been stable for at least 6–12 months, with the water parameters consistently in the SPS-appropriate range, with the lighting and flow dialed in, and with the husbandry routine established. The SPS coral in an unstable tank is the SPS coral that is dying.
The water parameters that the SPS coral requires
Before I describe the species, I want to establish the water parameters that the SPS coral requires, because the species-appropriate parameters are the foundation of the SPS husbandry.
The alkalinity. The SPS coral requires an alkalinity of 7.5–9.0 dKH, with a stability of ±0.3 dKH or better. The alkalinity is the most important parameter for the SPS coral, and the alkalinity swings are the most common cause of SPS tissue loss. The alkalinity should be measured 2–3 times per week, and the alkalinity should be maintained with a dosing system (a two-part calcium/alkalinity doser, or a calcium reactor for larger tanks).
The calcium. The SPS coral requires a calcium of 380–450 ppm, with a stability of ±10 ppm or better. The calcium is consumed along with the alkalinity (the SPS coral deposits both in the calcium carbonate skeleton), and the calcium should be dosed to match the alkalinity dosing.
The magnesium. The SPS coral requires a magnesium of 1,300–1,400 ppm, with a stability of ±30 ppm or better. The magnesium is the silent stabilizer, and the magnesium is often the parameter that is forgotten until the alkalinity and the calcium start to swing unpredictably. The magnesium should be measured monthly and dosed as needed.
The nitrate. The SPS coral prefers a low nitrate, ideally below 5 ppm, but the SPS coral can tolerate a nitrate of 5–10 ppm (with some species, the coloration is actually enhanced by a low-but-not-zero nitrate). The SPS coral does not tolerate a high nitrate (>20 ppm), and the high nitrate is associated with the zooxanthellae overgrowth that produces the "brown jelly" tissue loss.
The phosphate. The SPS coral prefers a very low phosphate, ideally below 0.03 ppm, and the phosphate above 0.10 ppm is associated with the algae overgrowth that smothers the SPS tissue. The phosphate should be controlled with the appropriate filtration (a protein skimmer, a refugium with macroalgae, a phosphate-removing media like GFO or a lanthanum-based media).
The temperature. The SPS coral prefers a temperature of 76–78°F, with a stability of ±1°F. The temperature swings (a heater failure, a chiller failure, a room temperature swing) are catastrophic for the SPS coral, and the swings should be prevented with appropriate equipment (a heater with a thermostat, a chiller with a thermostat, a temperature controller that can fail-safe to one or the other).
The salinity. The SPS coral prefers a salinity of 1.025–1.026, with a stability of ±0.001. The salinity swings are catastrophic for the SPS coral, and the swings should be prevented with an auto top-off system that maintains the salinity.
The SPS tank is the tank that requires the most monitoring, the most equipment, and the most consistency. The SPS tank is not the tank for the owner who is not willing to invest in the equipment, the monitoring, and the consistency.
The starter species: the forgiving SPS
The starter SPS species are the species that tolerate more parameter variation, that are more forgiving of beginner mistakes, and that are more likely to survive the first year in the new SPS tank. The starter species are the species I recommend for the keeper who is moving from LPS to SPS for the first time.
Seriatopora hystrix (Bird's Nest Coral). The most forgiving SPS species. The bird's nest grows rapidly (1–2 inches per month under good conditions), is tolerant of a wider range of water parameters (alkalinity 7.0–10.0, calcium 380–480, magnesium 1,250–1,450), and recovers well from minor parameter swings. The bird's nest comes in a range of colors (green, pink, yellow), and the bird's nest is the perfect "first SPS" species. The bird's nest prefers moderate to high lighting and moderate to high flow.
Pocillopora damicornis (Cauliflower Coral). Another forgiving SPS species. The cauliflower coral grows rapidly, is tolerant of parameter variation, and has a distinctive "cauliflower" appearance with bumpy branches. The cauliflower comes in green, pink, and brown color morphs, and the cauliflower is one of the easier SPS to frag (cut and propagate) once established.
Montipora digitata (Velvet Digital Coral). A plating or branching SPS that grows rapidly, has a beautiful velvet-like texture, and comes in a wide range of colors (green, orange, red, purple). The Montipora is more forgiving than many other SPS species, and the Montipora is a good "transition" species from the LPS world to the SPS world. The Montipora prefers moderate to high lighting and moderate to high flow.
Montipora capricornis (Plate Coral). A plating SPS that grows in horizontal plates, creating a beautiful "shelf" appearance in the reef. The plate coral is more forgiving than many other SPS species, and the plate coral is appropriate for the new SPS keeper. The plate coral prefers moderate to high lighting and moderate to high flow.
These four species are the starter kit for the new SPS keeper. The species are forgiving, they grow rapidly, they are visually attractive, and they provide the keeper with the experience of SPS husbandry without the risk of the more demanding species.
The intermediate species: the growing SPS
The intermediate SPS species are the species that are more demanding than the starter species, that require more stable parameters, and that are appropriate for the keeper who has successfully kept the starter species for 6–12 months and is ready for the next challenge.
Acropora millepora (Staghorn variant). A classic Acropora species, with a branching morphology and a wide range of colors (the "rainbow millies" are some of the most colorful SPS available). The millepora requires stable alkalinity (within 0.2 dKH), stable calcium, and stable magnesium, and the millepora does not tolerate the parameter swings that the starter species tolerate. The millepora prefers high lighting and high flow, and the millepora is one of the species that "tells you" when the parameters are off (the millepora's colors fade, the polyps retract, the growth slows).
Acropora tenuis (Staghorn Coral). Another classic Acropora species, with thin, branching branches and a delicate appearance. The tenuis requires the same stable parameters as the millepora, and the tenuis is somewhat more demanding than the millepora. The tenuis comes in a range of colors, and the tenuis is one of the most popular SPS species in the hobby.
Acropora yongei (Yongei Staghorn). A fast-growing Acropora with a delicate, branching morphology. The yongei is a good "intermediate" Acropora, with the growth rate of the starter species and the color potential of the more demanding Acropora species.
Stylophora pistillata (Smooth Cauliflower Coral). A SPS with a smooth, branching morphology, often confused with Pocillopora but with smoother branches. The Stylophora is more demanding than the Pocillopora, and the Stylophora requires more stable parameters. The Stylophora is a good intermediate species for the keeper who has mastered the starter Pocillopora.
These four species are the intermediate kit for the SPS keeper who is ready for the next challenge. The species are more demanding, more colorful, and more rewarding than the starter species, and the species provide the keeper with the experience of true Acropora husbandry.
The advanced species: the expert SPS
The advanced SPS species are the species that are the most demanding, the most colorful, and the most rewarding. The advanced species are appropriate for the keeper who has successfully kept the intermediate species for 6–12 months, who has the equipment and the monitoring in place, and who is ready for the apex of the SPS hobby.
Acropora microclados (Strawberry Shortcake Acropora). One of the most colorful Acropora species, with a striking pink-and-white coloration. The microclados is one of the most demanding SPS species, requiring very stable alkalinity, very stable calcium, very low nitrate and phosphate, and intense lighting and flow. The microclados is the species that experienced SPS keepers aspire to.
Acropora granulosa (Granular Staghorn). A classic Acropora with a distinctive granular texture and a range of colors. The granulosa is demanding in its parameter requirements, and the granulosa is the species that separates the experienced SPS keeper from the beginner.
Acropora tortuosa (Staghorn variant). A rare and highly sought-after Acropora with a striking blue or green coloration. The tortuosa is among the most demanding SPS species, and the tortuosa is appropriate only for the SPS keeper with the most stable tank and the most experienced eye.
Echinopora lamellosa (Christmas Tree Coral). An unusual SPS that grows in a branching, "Christmas tree" morphology, often with a striking green or red coloration. The Echinopora is a slow-growing, demanding species that is appropriate for the expert SPS keeper.
These four species are the apex of the SPS hobby. The species are the species that experienced SPS keepers grow after years of husbandry experience, and the species are the species that produce the most impressive display in the most experienced reef tanks.
The four mistakes that turn a stable SPS tank into a crash
Mistake 1: Adding the SPS too early. The most common mistake. The keeper has a new reef tank, the keeper is excited about the SPS, and the keeper adds the SPS to the tank before the tank is stable. The SPS in an unstable tank is the SPS that is dying. The fix is to wait at least 6–12 months after the tank is established before adding the SPS, to verify that the water parameters are stable (alkalinity, calcium, magnesium, nitrate, phosphate), and to add the starter species first, not the advanced species.
Mistake 2: Allowing alkalinity swings. The second most common mistake. The alkalinity swings by more than 0.5 dKH in a day, and the SPS reacts with tissue loss. The fix is to use a dosing system that maintains the alkalinity automatically, to test the alkalinity 2–3 times per week, and to address any alkalinity drift immediately.
Mistake 3: Inadequate lighting or flow. The third mistake. The SPS coral is in a tank with inadequate lighting (the SPS needs intense, full-spectrum lighting, typically 200+ PAR at the coral), or the SPS is in a tank with inadequate flow (the SPS needs strong, turbulent flow that prevents the boundary layer from forming on the coral surface). The fix is to verify the lighting and flow requirements of the specific species, and to upgrade the equipment as needed.
Mistake 4: Adding the SPS to a tank with a high nutrient load. The fourth mistake. The SPS is added to a tank that has a high nitrate (above 10 ppm) or a high phosphate (above 0.05 ppm), and the SPS is smothered by the algae and cyanobacteria that thrive in the high-nutrient environment. The fix is to bring the nutrients down before adding the SPS, with appropriate filtration (a protein skimmer, a refugium, a phosphate-removing media), with appropriate water changes, and with appropriate feeding reduction.
The bottom line
The SPS coral is the apex of the reef-keeping hobby, and the SPS coral is the coral that demands the most from the keeper. The right species for the keeper depends on the keeper's experience, the tank's stability, and the keeper's commitment to the husbandry. The starter species (Seriatopora, Pocillopora, Montipora) are the species for the new SPS keeper. The intermediate species (Acropora millepora, tenuis, yongei, Stylophora) are the species for the keeper with 6–12 months of SPS experience. The advanced species (Acropora microclados, granulosa, tortuosa, Echinopora) are the species for the keeper with years of experience and a stable tank.
The four mistakes — adding the SPS too early, allowing alkalinity swings, inadequate lighting or flow, and adding the SPS to a high-nutrient tank — are the most common ways that the SPS tank crashes. The fix in each case is awareness, planning, and patience. The SPS coral is the coral that rewards the patient and the prepared. The SPS coral is the coral that punishes the impatient and the unprepared. The difference is the preparation. The preparation is the framework above. The framework, applied with discipline, is the right prevention.
The keeper who has the patience, the equipment, and the commitment to the SPS husbandry is the keeper who has the most impressive display in the reef hobby. The keeper who is not prepared is the keeper who has the most discouraging SPS melt. The difference is the preparation. The preparation is the framework above. The framework, applied with discipline, is the right prevention.
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About the author
Olivia Brown is a long-time reef hobbyist and consultant with 15+ years of experience ranging from nano-reefs to 300-gallon mixed reef systems. She has worked with both hobbyists and small commercial aquaculture operations on tank cycling, husbandry, equipment selection, and long-term system design, with a particular focus on the demanding SPS coral husbandry that requires the most stable parameters and the most consistent maintenance. She writes regularly on the practical realities of keeping the most demanding reef species healthy and thriving.
