When building your first reef tank, it’s tempting to add all your favorite corals at once. But not all corals get along. Some species are aggressive, releasing stinging tentacles or toxins, while others are more peaceful. Understanding coral compatibility is key to maintaining a thriving, harmonious tank.
Peaceful Corals
Tend to coexist without attacking neighbors.
Example: Zoanthids, Mushrooms, Ricordea, Kenya Tree.
Best for beginners due to low aggression and ease of care.
Aggressive Corals
May deploy long sweeper tentacles at night to sting competitors.
Can outcompete others for light and space.
Examples: Galaxea, Euphyllia (Torch, Hammer), Favia, Hydnophora.
Chemical Warfare (Allelopathy)
Soft corals (e.g., Sinularia, Leather corals) may release toxins.
Toxins can inhibit growth or kill other corals.
Activated carbon and water changes help mitigate this.
Coral Type | Safe With | Avoid Pairing With |
|---|---|---|
Zoanthids | Mushrooms, Ricordea, LPS | Galaxea, Torch, Favia |
Mushrooms | Leathers, Kenya Tree | SPS, Euphyllia |
Euphyllia (Torch, Hammer) | Other Euphyllia (with space) | Acropora, Zoanthids |
Acropora (SPS) | Other SPS with space | LPS with long sweepers |
Favia/Favites | Peaceful LPS with buffer space | Soft corals |
Leather Corals | Most soft corals | SPS, due to chemical toxins |
Leave Proper Spacing:
Use 3–6 inches of space between aggressive and peaceful corals.
Observe Night Behavior:
Many corals extend sweepers at night. Observe after lights out.
Use Physical Barriers:
Frag racks or separate rocks can help contain aggressive species.
Run Activated Carbon:
Helps absorb toxins released by soft corals.
Stable Water Conditions:
Stressed corals may become more aggressive or vulnerable.
Acclimate New Corals Separately:
Give them time to adjust in a frag rack or quarantine zone.
Bleached or retracted polyps near another coral
Tissue damage or skeleton exposure
Excess slime or mucus on coral surfaces
Strong odors in tank (from toxins)
Detritus buildup or brown jelly near coral bases
Understanding coral compatibility allows you to build a balanced, thriving reef. By researching aggression levels and placing corals wisely, you can prevent stress, loss, and chemical warfare. Remember—reef tanks thrive on planning, patience, and observation.
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