SPS Coral Types – An Intro To SPS Reefkeeping

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Small polyp stony (SPS) corals are the end goal for many reef hobbyists. In the wild, these corals, like the impressive staghorn coral, define marine ecosystems and house a plethora of life on the reef. In the aquarium, they can bring the same color and depth to the tops of rockwork that other large polyp stony (LPS) corals and soft corals cannot.

However, SPS corals are regarded as the most challenging species of coral to keep in the home aquarium setting. While it is true that they are more difficult than other types of common coral, they are not completely out of reach for more serious hobbyists.

What Is The Difference Between Other Corals?

SPS corals are easy to identify. They completely lack the fleshy, large colony quality that LPS and soft corals have. Instead, SPS corals have a hard branched or plated appearance with individual polyps.

In the reef aquarium hobby, SPS are considered to be the most difficult species to keep, with LPS being for intermediate hobbyists, and soft corals being best for beginners. Apart from this, all three have very different anatomy and physiology.

SPS Corals

SPS corals, also known as hard corals, are responsible for building the natural reef. These animals excrete calcium carbonate skeletons that make structures for fish and invertebrates to find shelter; symbiotic zooxanthellae are also housed in these skeletons and complete photosynthesis which feeds the coral.

Taxonomically, SPS corals belong to the Scleractinia order1. From there, they are members of the Hexocorallia subclass which means that their polyp symmetry is divisible by six. Such as they are named, they have very small polyps on the outside of their flesh-covered calcium carbonate skeleton.

The calcium carbonate skeleton of SPS corals is built to withstand the battering from rough waves at the top of the reef where these corals are found. This also allows them to receive the most direct sunlight as their branches can grow for optimal exposure. This translates to a reef tank setting with the need for higher lighting and increased water flow.

Soft and LPS Corals

On the other hand, soft corals and LPS can be entirely fleshy, have a calcium carbonate skeleton, or contain sclerites, meaning they contain small pieces of hard internal structure; the main feature of soft corals and LPS corals though, is their very obvious polyps which can extend to impressive sizes.

Some LPS corals do have a calcium carbonate skeleton, however, the polyps extend outwards and don’t cover all parts of the structure such as they do for SPS. Some soft corals may contain sclerites but are much less structured than LPS overall.

Both LPS and soft corals are found lower down on the reef where the water current is not as strong and lighting is indirect. This translates into the aquarium with low to moderate lighting and moderate flow requirements for most species within these two categories.

Keeping Them In The Aquarium

SPS corals are notoriously known for being difficult to keep. But are they actually that much more demanding than other corals? Yes and no.

Yes, SPS corals are much more demanding than soft corals and LPS corals, but this doesn’t necessarily mean that they’re all more difficult. The main difference is the setup and the maintenance: SPS corals need a high-tech setup and stable conditions while LPS corals and soft corals can adapt to less optimal conditions.

A high-tech setup starts with good lighting, water flow, and filtration. SPS corals are some of the most light-demanding corals, and a good light fixture is necessary. This light needs to have a fully programmable spectrum, intensities, and photoperiod at the very least. The EcoTech Radion is a great example of an LED designed for the demands of an SPS tank.

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Water flow is almost, if not more, important than lighting. Water circulation keeps corals fed and prevents algae from taking over. Many SPS corals grow in tight colonies, which can cause dead zones in the densest parts. Water flow needs to be random in order to keep fresh water pushing past all areas of the colony at all times.

Though some reef aquarium hobbyists run SPS-dominant reefs with simple filtration, it is usually also a must to have a sump system. Sumps allow for additional room for beneficial bacteria to grow, increased nutrient export, and adequate aeration. All of these factors play into a more stable system overall.

Stability is arguably the most difficult part of keeping SPS. These corals are notorious for bleaching and eventually dying when conditions change too quickly. All major water parameters, along with alkalinity, calcium, magnesium, pH, salinity, and temperature all need to be constant for success.

Many hobbyists regulate these parameters with digital monitors, auto top-offs, and doser pumps, even Calcium reactors for full high end systems. These all get get very expensive over time. However, if you’re willing to spend the money upfront for a top-of-the-line SPS system, then there is a good chance that you will succeed in keeping these corals. Of course, you may do everything right but still have problems.

Water Parameters

That being said, what are the perfect water parameters for an SPS reef tank?

As always, these values can differ between tanks and hobbyists have had luck below and above the listed ranges; if your water parameters and tank conditions do not match these but your corals are healthy, do not attempt to change your system just to meet ‘ideal’ numbers.

In general, though, these are the accepted ranges for keeping SPS corals:

  • Lighting – High (200+ PAR)
  • Flow Rate – High
  • Temperature Range – 76-82 F
  • pH Range – 8.0-8.4
  • Salinity – 1.025 and 35 PPT 
  • Alkalinity – 8 dKH
  • Calcium Level – 350-450 PPM
  • Magnesium Level – 1200-1350 in PPM

Note that many hobbyists keep SPS corals in lighting conditions well over 200 PAR, though this is considered to be the bare minimum for attempting them at all.

Temperament In The Aquarium

One of the good things about SPS is that they are not very aggressive corals. This allows multiple species to be housed very closely together without too many problems; this does not mean that they will not try to sting each other though, so it is always best to be cautious and to trim any corals that grow too close together.

The main problem with SPS aggression is with other corals. LPS corals with long sweeper tentacles are very capable of stinging sessile SPS, which can quickly cause tissue loss and other damage. To prevent this, simply keep LPS away from SPS, possibly at another level of the tank.

Though SPS is usually able to regrow once the problem has been addressed, this still gives time for algae to takeover exposed skeleton which can impact the overall health of the coral.

What Is The Easiest Type To Keep?

Though SPS corals are more difficult to keep than most corals, there are a few that are easier than others. This includes Montipora and species from the Pocilloporidae family.

Frags of these corals are also usually cheap and easy to find, which can make the transition into keeping these corals a little less daunting.

When Can You Add Them To The Aquarium?

SPS corals need stability. The time for each reef aquarium to reach stability differs, but it is generally advised to not attempt keeping SPS corals until the system is at least one year old.

This time should allow for water parameters to settle, algae blooms to be controlled, and new soft and LPS coral growth to begin. Also, keep in mind that some species of SPS might do better than others, and do not get discouraged if one species doesn’t grow at all in your tank; this may be temporary, or your system will simply not support that kind of coral.

Common Types (Different Species)

SPS corals make up the ‘ideal reef’ that many envision when they think about a coral reef in the ocean; SPS are branching corals that give reefs their signature appearance. However, different species of SPS corals can be difficult to tell apart to the untrained eye. This could be due to a few reasons.

One, SPS are usually sold as small frags, which can make exact identification nearly impossible with such a small sample. Secondly, species of SPS can vary greatly in color and shape across the genus; as we’ll see, Montipora especially can come in several formations.

It should also be said that SPS-keeping is another level of the aquarium hobby. You will often come across corals that you have never seen before and might never see again. In general, it is best to know the general attributes of each major SPS genus and try to apply them to what you see.


Montipora Cap Coral

The Monti Cap coral is a good stepping stone to serious SPS reefkeeping. Becomes large and grows very fast

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  • Scientific Name: Montipora spp.
  • Difficulty Level: Easy-Moderate
  • Temperament: Not aggressive
  • PAR Requirements: Moderate (150 PAR)
  • Flow Requirements: Moderate-High
  • Placement: Middle, High
  • Origin: Indo-Pacific

Montipora is a genus of SPS corals with very diverse members. These corals can come in branching, plating, and encrusting varieties in almost all colors. They are not overly demanding in regards to being an SPS coral, but they do require high lighting, good flow, and stable water parameters just as the other, more advanced corals on this list do.

The most common types of Montipora to come across are Montipora digitata and plating Montipora.

Montipora Varieties

Montipora digitata is a branching variety of Montipora. The two most common colors are orange (‘Forest Fire Montipora digitata‘) and green (‘Green Montipora digitata‘); these corals have been modified to express the best colors and may be assigned a designer name.

Montipora digitata have thicker branches that sometimes grow together to form antler-like structures. Their polyps are very concentrated and have a soft appearance. The tips of these branches will typically be bare and white where new skeleton growth is forming.

In comparison, plating varieties, like Green Montipora digitata, grow outwards in large circular disks. Similarly, the tips of these plates will be white with new growth.

All varieties of Montipora can be attractive to most hobbyists as they’re one of the easiest and fastest species of SPS to keep.

Pocilloporidae Family

  • Scientific Name: Pocillopora spp., Seriatopora spp., and Stylophora spp.
  • Difficulty Level: Easy-Moderate
  • Temperament: Not aggressive
  • PAR Requirements: Moderate (200+ PAR)
  • Flow Requirements: High
  • Placement: Middle, High
  • Origin: Indo-Pacific

Members of the Pocilloporidae family are largely known as bird’s nest corals due to their interweaving branching growth. They come in many colors and are said to be even easier to keep than Montipora, but still require SPS growing conditions.

There are three genera of bird’s nest coral commonly found in the aquarium hobby: Pocillopora, Seriatopora, and Stylophora.


Pocillopora have thick, stubby branches. They have a moderately fuzzy appearance and are most commonly found in greens and purples.

Due to their thick branching, these corals do best with higher rates of water flow.


Stylophora are very similar to Pocillopora. In fact, it is usually only possible to tell these two corals apart by looking at a full colony.

Stylophora also have rounded branches with moderately fuzzy polyps. However, the overall appearance of the colony tends to be more orderly and uniform than that of Pocillopora.


Seriatopora are largely known as the true bird’s nest corals of this family as they have pointed tips and very thin branches that create an intricate twig-like cluster of coral. These corals are also most commonly found in pinks, greens, and purple and green combinations; their polyps are much more spread apart than the other related corals.

Seriatopora are very delicate and need to be handled with care. This can make fragging them very easy but can also make transportation quite difficult for larger colonies.


Acropora Coral

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The Acropora Coral is considered the pinnacle coral to keep in reef tank hobby. Difficult to care for, but extremely rewarding and easy to frag

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  • Scientific Name: Acropora spp.
  • Difficulty Level: Hard
  • Temperament: Not aggressive
  • PAR Requirements: Moderate (200+ PAR)
  • Flow Requirements: High
  • Placement: Middle, High
  • Origin: Indo-Pacific with some species in the Caribbean

Acropora are the end goal of many intermediate and advanced reefers. These corals are seen as some of the most difficult, yet most rewarding species in all of the hobby. There are many types of Acropora to choose from that come in nearly all colors, including more exclusive designer names.

Even though there are many different kinds of Acropora, they are still relatively easy to identify. These corals branch and have very identifiable polyps; each polyp has its own little tube that gives the coral a bumpy appearance. The actual polyps can be long and stringy or short and flat.

Acropora are considered the most difficult because they are easily affected by changes in water parameters. They also demand the most light and water flow out of all these species.

Closing Thoughts

SPS corals are thought to be some of the hardest, yet some of the most rewarding species of coral available in the aquarium hobby. Though this is true, their actual requirements aren’t as challenging as you might think. Instead, it’s their need for stability and consistency that can make their care extra difficult.

Luckily, there are a few easier species, like Montipora spp. and members from the Pocilloporidae family, that can make the transition from LPS corals and soft corals to Acropora a little less intimidating.

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