Corals may look stationary, but many of them are actively competing for space — and that competition can seriously damage a neighboring coral if you're not planning for it.
The Short Answer
Many corals use sweeper tentacles, chemical warfare, or direct stinging cells to compete for space. Adequate spacing and a bit of research on known aggressive species is the best prevention.
Signs of Coral Aggression
- Tissue damage or recession on the side of a coral facing a neighbor
- A coral extending unusually long sweeper tentacles at night
- One coral consistently outcompeting or overgrowing another nearby
How to Prevent It
- Research a coral's known aggression level before placing it near others — some species (certain LPS especially) are notably more aggressive than others.
- Leave generous spacing, more than you think you need, especially for corals known for long sweeper tentacles.
- Watch new additions closely for the first few weeks, since aggression often shows up as the coral settles in and starts extending fully.
- If you spot damage, increase spacing or relocate one of the corals rather than waiting for it to resolve on its own.
Not sure if two specific corals are safe to place near each other? Ask us before you commit to a layout — it's much easier to plan around aggression than fix it after the fact.
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