Established duncan colony suddenly losing polyps

[rwb500]

I've had this colony of duncans for over a year, it has maybe 60 polyps. Suddenly 2 days ago I noticed 3 polyps in one area had ejected their polyps and lost all of their tissue. Now it looks like there are other areas where there is tissue loss. I've done some extra water changes recently but other than that everything is normal. all parameters are within normal limits and all other corals (mixed reef) look perfectly normal. Any thoughts how to stop this?

 

[shwareefer]

It's better if you post your tank parameters rather than just saying 'normal' since most people will assume they are in fact not.

Duncans are the first to get ticked off when there's water quality issues. If you can't measure anything off and you haven't made any other changes to the system it might be a good time for an ICP test.

Any new additions that could have introduced a pest?

 

[Rick's Reviews]

Maybe they are just unhappy in that area? 3/60 loss is good I assume, I would not change anything and just monitor then review, it deffenitly does not hurt to ask but I would not worry at this stage, I deffenitly would not change anything and just monitor

 

[rwb500]

Temp 79, Alk 8, Cal 420, Mag 1300, nitrate 2, phos 0.03. I don't test pH. I recently added some fish that were quarantined with Prazipro. Otherwise no recent changes other than a few small water changes to suck out some algae. I rarely do water changes. The two tanks plumbed together total 200 gallons and plenty of other SPS, even more LPS, and a bunch of softies all look completely fine.

The colony has been in the same location with the same light and flow for over one year. It looks like more polyps are severely retracted and I fear the whole thing will die soon.

 

[mdb_talon]

I agree most of the remaining look quite stressed. If it were me I would run some carbon for awhile in case you do have toxin of some sort that got in there and send an ICP. Inspect for pests is probably an obvious step, but personally never found pests to be common on Duncan's.

Your nutrients seem pretty low and I would wonder if it's been a slow decline and they been starving?

 

[ccole]

Are you dosing any trace elements? You may have some trace deficiencies if you’re not and also not doing water changes often.

 

[Jmp998]

Any new fish that might be picking at it? This is exactly how my Duncan looks after adding my filefish which picks at it-all of the polyps retracted, polyps at the edges (the most picked at) dying.

 

[damsels are not mean]

Agree with above ^ If I were a duncan coral being eaten this is what I'd look like

 

[blaxsun]

I'm in the same boat with 2 small duncan colonies that all retracted a few weeks ago. It's either something in the water (but all the other corals are fine) or something's picking at it. I'm leaning towards the latter scenario.

 

[homer1475]

Certainly looks ticked off.

I would say it's normal, but typically you won't loose heads at the top. Normally you loose heads at the bottom that are being shaded out.

I have a rather large colony myself(somewhere around 100+ heads), and I loose heads all the time. But like I said, it's typically around the bottom that being shaded out by the rest of the colony.

What recent fish additions did you add? Someone could be picking on it.