Coral Compatibility Guide - Peaceful Reef Planning

Coral Compatibility Guide - Building a Peaceful Reef

One of the most important aspects of reef keeping is understanding coral compatibility. Corals compete for space, light, and resources - and some are more aggressive than others. This guide will help you plan your reef layout to minimize coral warfare and maximize the health and beauty of your tank.

Understanding Coral Aggression

Corals have evolved various defense and offense mechanisms to compete for space on the reef:

Aggression Methods

  • Sweeper tentacles: Extended tentacles (sometimes 6+ inches) that sting neighboring corals at night
  • Mesenterial filaments: Digestive strands released to digest nearby corals
  • Chemical warfare: Release toxins into the water to inhibit nearby coral growth
  • Overgrowth: Fast-growing corals can simply grow over slower neighbors
  • Shading: Tall corals block light from corals below

Coral Aggression Levels

Peaceful Corals (Low Aggression)

These corals rarely harm their neighbors and are safe to place near most other corals.

  • Zoanthids & Palythoas - Peaceful, but can overgrow slower corals
  • Mushroom corals - Very peaceful, minimal aggression
  • Leather corals - Peaceful but use chemical warfare (good skimming helps)
  • Xenia - Peaceful but spreads rapidly
  • Clove polyps - Peaceful but can spread
  • Green Star Polyps (GSP) - Peaceful but will encrust everything
  • Kenya Tree - Peaceful but drops fragments everywhere
  • Ricordea - Very peaceful
  • Montipora - Generally peaceful SPS
  • Birdsnest corals - Peaceful SPS

Moderately Aggressive Corals

These corals need some space and can harm immediate neighbors.

  • Duncan corals - Short sweepers (2-3 inches)
  • Acanthastrea (Acan) - Moderate sweepers
  • Micromussa - Can have sweepers
  • Blastomussa - Moderate aggression
  • Favites (Favia/Favites) - Moderate sweepers
  • Caulastrea - Short sweepers
  • Acropora - Can shade and overgrow
  • Stylophora - Moderate SPS aggression
  • Pocillopora - Can be aggressive to nearby SPS

Highly Aggressive Corals

These corals are territorial and need significant space from neighbors.

  • Hammer corals (Euphyllia ancora) - Long sweepers (6+ inches)
  • Torch corals (Euphyllia glabrescens) - Very long sweepers (6-12 inches)
  • Frogspawn (Euphyllia divisa) - Long sweepers (6+ inches)
  • Galaxea - Extremely aggressive, very long sweepers (12+ inches)
  • Goniopora - Long sweepers, aggressive
  • Alveopora - Similar to Goniopora
  • Bubble coral (Plerogyra) - Long sweepers at night
  • Elegance coral - Very aggressive sweepers
  • Chalice corals - Can be very aggressive
  • Trachyphyllia (Trachy) - Aggressive sweepers
  • Catalaphyllia (Elegance) - Very aggressive

Compatibility by Coral Type

Soft Corals with Other Corals

Soft corals + Soft corals: ✅ Generally compatible
Soft corals + LPS: ⚠️ Usually okay with spacing
Soft corals + SPS: ⚠️ Chemical warfare concerns - good skimming essential

Note: Leather corals release chemicals that can inhibit SPS growth. If keeping both, run a quality protein skimmer and use activated carbon.

LPS with Other Corals

LPS + LPS: ⚠️ Depends on species - watch for sweepers
LPS + Soft corals: ⚠️ Usually okay with spacing
LPS + SPS: ⚠️ Keep LPS sweepers away from SPS

Important: Many LPS have sweeper tentacles that extend at night. Always leave extra space!

SPS with Other Corals

SPS + SPS: ✅ Generally compatible, but watch for shading and overgrowth
SPS + LPS: ⚠️ Keep away from LPS sweepers
SPS + Soft corals: ⚠️ Chemical warfare concerns

Note: SPS corals can touch each other more safely than mixing with other types, but fast growers can still overgrow slower species.

Zoanthids & Palythoas

Zoas + Zoas: ✅ Very compatible
Zoas + Other corals: ✅ Generally peaceful, but can overgrow slower corals

Tip: Place zoas on separate rocks to prevent them from spreading onto other coral colonies.

Spacing Guidelines

Minimum Spacing Recommendations

Coral Type Minimum Space from Neighbors
Peaceful soft corals 2-3 inches
Zoanthids 2-3 inches (or separate rock)
Mushrooms 2-3 inches
Peaceful LPS (Duncan, Acan) 3-4 inches
Moderate LPS 4-6 inches
Euphyllia (Hammer, Torch, Frogspawn) 6-8 inches minimum
Galaxea 12+ inches (isolate if possible)
Goniopora/Alveopora 6-8 inches
Chalice corals 4-6 inches
SPS corals 2-4 inches (for growth room)

Remember: These are minimums - more space is always better!

Special Compatibility Notes

Euphyllia Family Exception

Hammers, torches, and frogspawn from the Euphyllia family can often touch each other without issues, even though they're aggressive to other corals. However:

  • Different species may still sting each other
  • Watch closely when placing them near each other
  • Some individuals are more aggressive than others

Acropora Compatibility

Different Acropora species can generally be placed close together, but:

  • Fast-growing species will shade slower ones
  • Branching types need room to grow
  • Table Acros will shade everything below

Zoanthid Spreading

While peaceful, zoanthids spread rapidly and can:

  • Overgrow slower-growing corals
  • Spread across rock work
  • Be difficult to remove once established
  • Solution: Place on isolated rocks or create barriers

Green Star Polyps (GSP)

GSP is incredibly peaceful but will encrust everything:

  • Can cover entire rock structures
  • Will grow onto glass, equipment, other corals
  • Solution: Place on isolated island rock surrounded by sand

Tank Layout Strategies

Zoning Your Reef

Organize your tank into zones based on aggression levels:

Peaceful Zone

  • Mushrooms, zoanthids, ricordea
  • Can be placed closer together
  • Good for beginners

Moderate Zone

  • Most LPS, peaceful SPS
  • Moderate spacing required
  • Monitor for sweepers

Aggressive Zone

  • Euphyllia, Galaxea, aggressive LPS
  • Isolated with plenty of space
  • Keep away from other corals

Vertical Placement Strategy

Use height to your advantage:

  • Top third: SPS corals (high light, less sweeper risk)
  • Middle third: Moderate LPS, some soft corals
  • Bottom third: Peaceful corals, mushrooms, low-light species

This vertical separation helps prevent sweeper tentacle contact.

Island Rock Method

For aggressive spreaders (GSP, xenia, Kenya tree):

  • Place on separate rock surrounded by sand
  • Prevents spreading to main reef structure
  • Easy to remove if needed
  • Creates visual interest

Monitoring for Coral Warfare

Signs of Coral Aggression

  • Tissue recession: Coral tissue pulling back from contact point
  • Bleaching: White areas where corals touch
  • Brown jelly: Bacterial infection from coral stings
  • Closed polyps: Coral staying closed on one side
  • Slow growth: Coral not growing toward aggressive neighbor

What to Do if Corals Fight

  1. Separate immediately: Move one or both corals
  2. Increase spacing: Add several more inches of space
  3. Monitor damage: Watch for tissue recession or infection
  4. Consider barriers: Use rock structures to block sweepers
  5. Dip if needed: Coral dip can help prevent infection

Beginner-Friendly Compatibility Combinations

Peaceful Reef (Easiest)

  • Zoanthids
  • Mushroom corals
  • Ricordea
  • Duncan corals (with space)
  • Green Star Polyps (on island rock)
  • Leather corals

Mixed Reef (Moderate)

  • Various zoanthids
  • Mushrooms
  • Duncan corals
  • Acans (with space)
  • Hammer or Torch (isolated)
  • Montipora SPS

SPS-Dominant Reef (Advanced)

  • Various Acropora
  • Montipora
  • Birdsnest
  • Stylophora
  • Pocillopora
  • Minimal LPS (well-spaced)

Common Compatibility Mistakes

1. Placing Galaxea Too Close

The mistake: Underestimating Galaxea's 12+ inch sweepers
The result: Neighboring corals get stung and die
The fix: Isolate Galaxea with massive spacing or don't keep it

2. Euphyllia Near Other Corals

The mistake: Placing hammers/torches too close to non-Euphyllia
The result: 6+ inch sweepers damage neighbors at night
The fix: Give Euphyllia 6-8 inches minimum space

3. GSP on Main Rock Structure

The mistake: Placing GSP on your main reef structure
The result: GSP encrusts everything, impossible to remove
The fix: Always place GSP on isolated island rocks

4. Ignoring Nighttime Sweepers

The mistake: Not checking tank at night for extended sweepers
The result: Missing aggressive behavior that only happens in darkness
The fix: Check your tank at night with a flashlight occasionally

5. Mixing Soft Corals and SPS Without Carbon

The mistake: Keeping leather corals and SPS without chemical filtration
The result: SPS growth stunted by soft coral toxins
The fix: Run quality protein skimmer and activated carbon

Advanced Compatibility Tips

Creating Barriers

  • Use rock structures to block sweeper tentacles
  • Create overhangs to protect corals below
  • Use coral plugs on different levels

Growth Planning

  • Research adult size before placing
  • Leave room for 2-3 years of growth
  • Plan to frag or move corals as they grow
  • Fast growers need more initial space

Water Flow Considerations

  • Strong flow can push sweepers away from neighbors
  • Random flow patterns help prevent constant contact
  • Don't rely on flow alone - spacing is still critical

Compatibility Quick Reference Chart

Coral Type Safe With Caution With Avoid Near
Zoanthids Most corals Slow growers (may overgrow) -
Mushrooms All corals - -
Leather corals Soft corals, LPS SPS (chemical warfare) -
Duncan Most corals Nearby corals (short sweepers) -
Acan/Micromussa Most corals Immediate neighbors -
Hammer/Torch Other Euphyllia Everything else Most corals (long sweepers)
Galaxea - - Everything (extremely aggressive)
Montipora SPS, most corals Fast growers LPS sweepers
Acropora Other SPS Soft corals LPS sweepers

Final Thoughts

Coral compatibility is about understanding behavior and planning ahead. Key principles:

  • Research before buying: Know the coral's aggression level
  • Space generously: More space = fewer problems
  • Monitor regularly: Check for signs of warfare
  • Act quickly: Separate fighting corals immediately
  • Plan for growth: Leave room for corals to mature
  • Check at night: Many sweepers only extend in darkness

Ready to Build Your Reef?

Now that you understand coral compatibility, browse our collections and plan your peaceful reef:

More Resources

Remember: When in doubt, give more space. A little extra room now prevents problems later!