Look for reciprocal behaviour
Healthy courtship usually includes pauses, approach by both fish and continued normal swimming or feeding. One fish hiding constantly is not participating.
Identify escalation
- Torn fins or missing scales.
- A fish pinned to a corner or surface.
- Rapid breathing and refusal to eat.
- Repeated ramming or biting.
- No safe route away from a territory.
Use structure, not hope
Visual barriers, plants and multiple caves can reduce contact, but they cannot make an incompatible pair safe.
Separate early
Have a divider, net and cycled backup tank ready. Removing a fish before serious injury is better than waiting for a spawn.
Reassess the project
A pair that cannot coexist should not be forced together repeatedly.