Coral Groups: LPS, SPS, and Soft Corals
Coral Groups: LPS, SPS, and Soft Corals
Anyone planning their first reef aquarium quickly encounters three abbreviations: LPS, SPS, and soft corals. The division isn’t arbitrary — it describes real biological differences that directly affect what conditions corals require and how challenging they are to keep.
Understanding these differences before the first purchase saves a lot of frustration.
Why the Division Matters
A coral is an animal, but its structure and the way it obtains nutrition varies significantly between groups. These differences show up directly in their requirements:
- how much light and what kind
- how strong a flow suits them
- what nutrient levels (phosphate, nitrate) are optimal
- how sensitive they are to parameter swings
The same tank isn’t automatically suitable for all groups. An SPS-dominant tank and an LPS-dominant tank can require quite different parameters — and a compromise between them doesn’t always serve either group optimally.
Soft Corals
Soft corals (Alcyonacea) form no hard calcium skeleton at all. Their structure is soft tissue reinforced with tiny calcium-containing structures (sclerites) for support. This makes them physically flexible — they sway in current and contract when stressed, but recover quickly.
Identification: soft, often leathery or fleshy structures. No visible hard skeleton even when the coral is retracted.
Typical species:
- Zoanthids (Zoanthus, Palythoa) — small, colorful colonial polyps
- Leather corals (Sarcophyton, Sinularia, Lobophytum) — leathery, often brownish or cream-colored
- Mushroom corals (Discosoma, Rhodactis) — solitary, disc-shaped polyps
- Xenia and Anthelia — pulsing, branching soft forms
Why they’re the easiest starting point: soft corals tolerate parameter variation better than LPS or SPS. They recover quickly from stress, often grow vigorously, and give beginners time to learn tank management without constantly risking expensive animals. Many soft corals thrive in a reasonably imperfect tank.
Note: some soft corals — especially zoanthids and palythoa — contain palytoxin, a serious health hazard. Gloves are mandatory when handling them.
LPS — Large Polyp Stony Corals
LPS stands for Large Polyp Stony. These corals have a hard calcium skeleton with one or more large, fleshy polyps living on top. The polyp is large relative to the skeleton — when extended it can expand to many times the size of the skeletal base.
Identification: a clearly visible hard skeleton when the coral is retracted or dry. Polyps are large and fleshy when open.
Typical species:
- Euphyllia genus: hammer (E. ancora), frogspawn (E. divisa), torch (E. glabrescens) — long, round or branching tentacles
- Acanthastrea and Micromussa — colorful, encrusting colonies
- Brain corals (Platygyra, Favia, Favites) — round, ridged surface patterns
- Trachyphyllia — solitary, often red or green, lives in sand
- Goniopora — long, flower-like polyps
Requirements in brief: LPS does well with moderate light and flow — it doesn’t need the intensity SPS demands, but won’t thrive in dim conditions either. It’s more forgiving on nutrients than SPS: slightly elevated phosphate or nitrate won’t kill LPS, and some species actually prefer a bit more nutrient availability. LPS feeds readily — tentacles catch zooplankton, and larger species accept meaty food.
SPS — Small Polyp Stony Corals
SPS stands for Small Polyp Stony. The structure is the same as LPS — a hard calcium skeleton — but the polyps are tiny, often just a few millimetres across, covering the entire skeleton surface in a dense mat.
Identification: hard skeleton, usually branching or plating. Tiny polyps are best seen with good eyesight or at close range.
Typical species:
- Acropora — the most common and diverse SPS genus, branching or plating forms
- Montipora — plating or branching, often violet, green, or orange
- Stylophora — compact, rounded branching forms
- Seriatopora — thin, delicate branches
- Pocillopora — densely branching
Why they’re the most demanding: SPS corals are sensitive to parameter swings, especially alkalinity and calcium. They require high light, strong flow, and very low nutrient concentrations. Even a small persistent deviation in parameters shows up as slowed growth, color shift, or tissue loss. SPS is the group where hobbyists learn the most — and lose the most if they make mistakes.
Summary Table
| Soft Corals | LPS | SPS | |
|---|---|---|---|
| Light | low–moderate | moderate | high |
| Flow | low–moderate | moderate | strong |
| Nitrate | 5–20 ppm | 2–10 ppm | 0.5–5 ppm |
| Phosphate | 0.05–0.3 ppm | 0.02–0.1 ppm | 0.02–0.05 ppm |
| Difficulty | easy | intermediate | demanding |
| Sensitivity to change | low | moderate | high |
| Feeding | minimal | benefits from feeding | minimal |
Values are guidelines. There is considerable variation between species.
The Order to Approach Them
Most experienced hobbyists recommend the same progression: start with soft corals, move to LPS, and only then tackle SPS.
This isn’t a rule — it’s accumulated experience. Soft corals teach the basics of tank management without constant stress. LPS teaches the importance of parameters and feeding. SPS requires all of the above plus a stable, well-established tank. A hobbyist who jumps straight to SPS will learn — but usually through an expensive mistake.
For practical details on parameters by group, placement, and keeping multiple groups together, see the practice article.
References
Literature
- Borneman, E. H. (2001). Aquarium Corals: Selection, Husbandry, and Natural History. T.F.H. Publications.
- Delbeek, J. C., & Sprung, J. (1994). The Reef Aquarium, Vol. 1. Ricordea Publishing.
- Delbeek, J. C., & Sprung, J. (2005). The Reef Aquarium: Science, Art, and Technology, Vol. 3. Ricordea Publishing.
Community resources
- Reef2Reef Community. Coral identification and care guides. https://www.reef2reef.com
- Manta Systems (2025). Amino Acid, Carb & Vitamin Dosing in Reef Tanks. https://www.mantasystems.net/a/blog/post/amino-acids