Duncan issue

Good evening. I am an experienced reefer. Eh….i can measure in decades now but it doesn’t mean I know everything.
I have 2 beautiful Duncan colonies.
About 2 weeks ago my SG was 1.025. No big. I raised it to 1.026 in a water change. Not abnormal think it was about that time both colonies closed up.
This tank is a fully stocked mixed reef. I have softies LPS and SPS acros.
That was 2 weeks ago. My large colony is open and looks good but not quite as full like usual. Still nice.
The small colony has been closed almost 2 weeks. Pretty tight. Just little whiskers hanging out. But 4 of the heads have wide open mouths. Honestly I have never seen this before.
I run a high nutrient tank. 200gallon with lots of fish that eat lots of food and created lots of waste. While my nutrients are high I do not have algae’s or bacteria blooms.
Every tank I have ever had have high nutrients.

Anyway…..experienced thoughts would be appreciated.


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What are your other water parameters? I've never kept Duncans so, someone else may have some better thoughts than anything I come up with ;)
I can’t say I’ve ever seen that before. But I’ve never had success with Duncan’s either
Duncans can be hardy but they also are very close to NPS and really like lower light and food.

They do seem sensitive to changes especially lighting.

That said I have no idea why a change in salinity would do this. I have seen this with exact thing when to much lighting is added or starving.

What do you mean by high nutrients? Too high of nitrate or phosphate can be bad for corals even if you do not have algae..

I recently had to destroy a large colony because it got to big. After that I upgraded my lightning and the fragged heads did the same thing you are talking about and once I moved the fragged part to a slightly shaded area it is coming back.

I also had one in Sandys nano with no filtration and it did the same thing. I could not figure out why. That tank is higher nutrients and rely only on water changes. Its tentacles got short and slowly got smaller. It lasted years like that though. Maybe this coral is more sensitive to higher nutrients.
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strange, im running very low nutrients (3 no3 0.04 po4) and my duncan gets about 300 par, never had an issue..
i do feed it from time to time
My duncans are acting up too, or well .. even weirder, just one head is and I don´t understand why one looks fine and the other isn´t.

I don´t know if that is similar to yours?
My duncans are acting up too, or well .. even weirder, just one head is and I don´t understand why one looks fine and the other isn´t.
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I don´t know if that is similar to yours?

Looking at your picture it looks like you have something growing around yours, Maybe they are being irritated. I can not tell from the picture if it is some hair algae, bacteria maybe even chrysophyes.
So,mine are dying. The heads are too close together to reliably frag out. Maybe I will get lucky. Idk. I chalk it up to survival of the fittest. We’re playing god with this stuff. Nothing is forever.
The other colony I have has close to 20 heads. I’m changing my water. Otherwise the thing is pretty big.