How to kill pulsing xeina

[AquaPin]

For Aptasia I killed it with a syringe of vinegar injected into the base, I would try that.

Back in the day before knowing better I too introduced xenia to my tank and it spread rapidly. I was "lucky" to have a hammer colony fall on the xenia and it killed most if it. The last little bit I chiseled out. If you do not kill/pull right to the base it will return.