Hard corals are the foundation of natural coral reefs and among the most sought-after livestock in the marine aquarium hobby. Their incredible colours, growth forms, and reef-building abilities make them the centrepiece of many advanced reef aquariums.
Unlike soft corals, hard corals build calcium carbonate skeletons that require stable water chemistry, strong lighting, and appropriate water flow to thrive. While some hard corals are suitable for beginners, others demand a higher level of reef-keeping experience.
In this guide, we'll explain everything you need to know about keeping hard corals successfully, including the differences between SPS and LPS corals, lighting requirements, water chemistry, feeding, placement, and long-term care.
What Are Hard Corals?
Hard corals are stony corals that produce rigid calcium carbonate skeletons.
These corals are responsible for building the reef structures found throughout the world's oceans.
In reef aquariums, hard corals are generally divided into two groups:
- LPS Corals (Large Polyp Stony Corals)
- SPS Corals (Small Polyp Stony Corals)
Both require calcium, alkalinity, and magnesium to build and maintain their skeletons.
Why Keep Hard Corals?
Hard corals offer some of the most spectacular colours and growth patterns available in reef keeping.
Benefits include:
- Incredible colouration
- Unique growth forms
- Reef-building behaviour
- Long-term colony development
- High visual impact
Many reef aquarists consider growing healthy hard corals to be one of the most rewarding aspects of the hobby.
Understanding LPS Corals
LPS corals feature large fleshy polyps attached to a calcium skeleton.
Popular LPS corals include:
Euphyllia Corals
Examples include:
- Torch Corals
- Hammer Corals
- Frogspawn Corals
These are known for their flowing movement and vibrant colours.
Acan Corals
Acanthastrea corals are colourful and relatively easy to care for.
Blastomussa
Blastomussa corals produce large fleshy polyps and are suitable for a wide range of reef aquariums.
Duncan Corals
Duncan corals are often recommended for beginners due to their hardiness and feeding response.
Candy Cane Corals
A popular LPS coral known for its ease of care and attractive appearance.
Understanding SPS Corals
SPS corals have small polyps and typically form branching or plating structures.
Popular SPS species include:
Acropora
Acropora corals are often considered the pinnacle of reef keeping.
Known for:
- Intense colouration
- Fast growth
- High lighting demands
Montipora
Montipora species are often more forgiving than Acropora.
Common forms include:
- Plating Montipora
- Encrusting Montipora
- Branching Montipora
Birdsnest Corals
Birdsnest corals are colourful, fast-growing SPS corals suitable for intermediate reef keepers.
Stylophora and Pocillopora
These SPS species are often recommended as stepping stones into advanced SPS reef keeping.
Water Parameters for Hard Corals
Hard corals demand stability above all else.
Recommended parameters include:
| Parameter | Recommended Range |
|---|---|
| Temperature | 24-26°C |
| Salinity | 1.025-1.026 SG |
| pH | 8.1-8.4 |
| Alkalinity | 7-9 dKH |
| Calcium | 400-450 ppm |
| Magnesium | 1250-1400 ppm |
| Nitrate | 2-15 ppm |
| Phosphate | 0.02-0.1 ppm |
Rapid fluctuations are often more damaging than slightly imperfect numbers.
Calcium, Alkalinity and Magnesium
Hard corals consume minerals continuously as they grow.
Calcium
Required for skeletal growth.
Target:
- 400-450 ppm
Alkalinity
Supports coral growth and biological stability.
Target:
- 7-9 dKH
Magnesium
Helps stabilise calcium and alkalinity.
Target:
- 1250-1400 ppm
Regular testing is essential in hard coral aquariums.
Lighting Requirements
Lighting is one of the most important factors for successful hard coral keeping.
Popular reef lighting systems include:
- Ecotech Radion
- AI Hydra
- Red Sea ReefLED
- Kessil LED
- Reef Factory Reef Flare
Typical PAR Requirements
| Coral Type | PAR Range |
| LPS Corals | 75-200 |
| Montipora | 150-300 |
| Acropora | 250-450 |
| Birdsnest | 200-350 |
Always acclimate corals to new lighting gradually.
Water Flow Requirements
Strong, random flow is essential for hard corals.
Benefits include:
- Oxygen delivery
- Waste removal
- Nutrient transport
- Improved growth
Modern wave pumps such as:
- Ecotech Vortech
- AI Nero
- Tunze Stream
- Maxspect Gyre
allow reef keepers to create natural flow patterns.
LPS Corals
Prefer:
- Moderate flow
- Gentle movement
SPS Corals
Prefer:
- Strong turbulent flow
- Random flow patterns
Feeding Hard Corals
Although photosynthesis provides much of their energy, many hard corals benefit from supplemental feeding.
Suitable foods include:
- Reef Roids
- Zooplankton
- Amino acids
- Coral foods
- Frozen plankton
LPS corals generally display stronger feeding responses than SPS corals.
Coral Placement Guide
Bottom of Aquarium
Suitable for:
- Blastomussa
- Acan Corals
- Certain Euphyllia
Mid-Level
Suitable for:
- Duncan Corals
- Candy Cane Corals
- Hammer Corals
Upper Areas
Suitable for:
- Acropora
- Montipora
- Birdsnest Corals
Placement should always reflect lighting and flow requirements.
Dosing for Hard Corals
As coral growth increases, mineral consumption rises.
Common dosing methods include:
Two-Part Dosing
Adds:
- Calcium
- Alkalinity
Three-Part Dosing
Adds:
- Calcium
- Alkalinity
- Magnesium
Balling Method
Popular among advanced reef keepers.
Calcium Reactors
Suitable for larger reef systems with significant coral demand.
Coral Acclimation
When introducing new hard corals:
- Match temperature.
- Drip acclimate if necessary.
- Dip corals to remove pests.
- Start in lower light areas.
- Gradually move to final placement.
Proper acclimation reduces stress and improves long-term success.
Common Hard Coral Problems
Tissue Recession
Possible causes include:
- Parameter instability
- Low flow
- Pests
Bleaching
Often caused by:
- Excessive lighting
- Temperature spikes
- Water chemistry issues
Poor Colouration
Can result from:
- Nutrient imbalance
- Insufficient lighting
- Trace element deficiencies
Slow Growth
Often linked to:
- Low alkalinity
- Low calcium
- Inadequate flow
Hard Coral Pests
Regular inspections are essential.
Common pests include:
- Acropora Eating Flatworms
- Red Bugs
- Nudibranchs
- Vermetid Snails
Quarantining and dipping new corals helps reduce risk.
Best Hard Corals for Beginners
If you're moving from soft corals into hard corals, consider:
Beginner LPS Corals
- Duncan Coral
- Candy Cane Coral
- Blastomussa
- Acan Coral
Beginner SPS Corals
- Montipora
- Birdsnest
- Stylophora
- Pocillopora
These species are generally more forgiving than Acropora.
LPS vs SPS Corals
| LPS | SPS |
| Large fleshy polyps | Small polyps |
| Moderate lighting | High lighting |
| Moderate flow | Strong flow |
| Easier care | More demanding |
| Direct feeding benefits | Mostly photosynthetic |
Many successful reef tanks contain both groups.
Building a Hard Coral Reef Aquarium
Successful hard coral systems typically include:
- High-quality lighting
- Powerful water movement
- Stable salinity
- Consistent dosing
- Efficient nutrient export
- Regular testing
Patience and consistency are key to long-term success.
Final Thoughts
Hard corals represent some of the most beautiful and rewarding animals available to marine aquarists. While they require greater attention to water chemistry, lighting, and flow than many soft corals, the results can be spectacular.
Whether you're growing colourful LPS corals or building a thriving SPS-dominated reef, maintaining stability and understanding the specific needs of each coral species will help ensure long-term success.
With proper care, hard corals can develop into stunning colonies that transform a reef aquarium into a vibrant underwater ecosystem.
Need Help Choosing Hard Corals?
At Charterhouse Aquatics, we stock a wide range of LPS and SPS corals, reef lighting systems, dosing solutions, testing equipment, supplements, and coral foods to help you build a thriving reef aquarium. Our reef specialists can help you select the perfect corals for your aquarium and experience level.
