Last month I came home from work and detected the faint odor of 'coral' in my home (those who have handled or fragged live coral should know this smell). I asked my wife if she had used any chemical cleansers or aerosol freshners that day, and she had not.

A cursory visual check of my reef tank didn't reveal anything out of the ordinary but the water had a detectable coral smell, which is something that it has never emitted before.

The next day or so all of my anthellia (waving hand coral, a soft coral and type of xeniid) weren't looking well. This coral was widespread in my tank (to the point of being invasive) and every single polyp was looking deflated and shrivelled.

The following day things when from oddly bad to severely catastrophic.

Anthelia polyps each have 8 feathered tentacles. I had literally at least a good hundred+ anthelia polyps in the tank and not only were they all disintegrating but nearly all of them had shed all of their tentacles or fragments of their tentacles (which my powerheads were disseminating throughout the tank). Anthelia debris, and literally hundreds of anthelia tentacles were everywhere in my tank and the smell was horrid.

My skimmate collection cup was essentially an evil-smelling mass of chunky coral slime with anthelia fragments; the water column was cloudy. My trachyphyllia (open brain coral) and montipora were buried under anthelia fragments and were adversely affected from this physical contact. What ever toxins anthelia contained where being released and all of my euphyllia LPS corals were extremely retracted, almost looking like they no longer existed.

I had no SW on hand so I had to make some, it would take me several hours to create enough RO/DI water and then make the SW (at a minimum I needed 30gal for a 50% water change), I wouldn't be able to get started until about midnight.

In the mean time I netted out a lot of the anthelia debris. For some reason none of my even more widespread xenia was effected. The entire sandbed was littered with settled anthelia debris.

I got as much disintegrated coral as I could and placed 3 or 4 cups of high-grade carbon in my canister filter. I repeated the process a couple of days later and then again during the next couple of weekends (50% water change, copious amounts of high grade carbon) to restore the quality of my water.

Up until this point anthelia had been an indestructable, hardy, fast spreading coral, practically weed-like in my tank (I've had it since 2006), and the entire population was practically decimated. I have not figured out what the cause of this was, why just anthelia was directly effected, or why it was a simultaneous tank-wide decimation rather than a localized one. My water parameters were all within the norms.

Two small anthelia polyps managed to survive unscathed, adjacent to a third polyp which is just a stalk, having lost all of its tentacles. This tiny survivor group appears to be making a speedy come back, and today (3 weeks following the meltdown) numbers nine polyps.

Anthelia debris had coated my montipora and it seems to be on its way out (spreading irreversable tissue recession, no polyp extention and bleaching). My open brain coral was had also been submerged under anthelia debris and has become partially bleached and browned out, but it seems to be in much better shape than the montipora. A few candy cane polyps that were blanketed with anthelia-matter have lost some tissue (looking as if that had been stung). My euphyllia corals have regained their expansion. All other corals (soft, LPS, SPS) were apparently unaffected.

Maybe the huge anthelia population quickly depleted some vital element(s) in the water, I have no idea. One lesson learned is that I will treat any detectable odor of coral in the air or from the water as an immediate emergency. Maybe if I had done a 50% water change that very first day the situation could have been prevented or controlled somewhat.

Or maybe it just mysteriously crashed like its cousin the xenia seems to do for many other hobbyists (my xenia population seems to be has heathy as ever at this time though).