Aggressive Corals
Not all corals can be placed close together in a reef aquarium. Some corals are considered aggressive because they compete for space using sweeper tentacles, direct contact, or chemical warfare.
Understanding coral aggression is important when planning a mixed reef tank. Improper spacing can lead to tissue damage, poor extension, and coral loss.
What Makes a Coral Aggressive?
Aggressive corals usually defend their space in one or more of these ways:
- long sweeper tentacles
- direct stinging on contact
- chemical compounds released into the water
Because corals continue growing over time, even safe-looking placement can become a problem later.
Common Aggressive Corals
- Torch Coral (Euphyllia): can sting nearby corals and needs extra space
- Hammer Coral: moderate to strong aggression depending on placement
- Frogspawn Coral: can damage neighboring corals with sweeper tentacles
- Galaxea: one of the more aggressive LPS corals
- Favia and some brain corals: may sting nearby colonies at night
How Much Space Should Aggressive Corals Have?
As a general rule, aggressive corals should be placed with extra room around them.
- Minimum spacing: 5–10 cm
- More space recommended: for torch, galaxea, and larger LPS corals
Keep in mind that coral growth will reduce spacing over time, so leave more room than you think you need.
Which Corals Are Usually Safer?
Peaceful or lower-aggression corals often include:
- Zoanthus
- Mushroom corals
- Ricordea
- Kenya Tree coral
- Green Star Polyps
These corals are often easier to place in mixed reef aquariums, although fast growth can still create crowding problems.
Signs of Coral Aggression
- tissue recession on the side facing another coral
- corals staying closed near one another
- visible sweeper tentacles at night
- burned or damaged tissue after contact
How to Reduce Coral Warfare
- leave enough space between colonies
- avoid placing aggressive LPS next to delicate soft corals
- watch corals at night if possible
- reposition corals before they grow into each other
Related Guides
Last updated: 2026
This guide is maintained by ReefExclusive.
