What is this on my Paly

[SGreene]

Something fishy is going on in my tank. Seriously, only Paly are closed up. I have tones of Zoa and Paly and ONLY paly are closing up, Zoa look great. Here is a close up of one frag, what is this thing attached to the corals?

 

[djrice69]

What are your basic water parameters

 

[resortez]

Parameter numbers would help & equipment run down. Also tank inhabitants & any recent changes or additions.

 

[SGreene]

Specific Gravity -- 1.024 to 1.026
Temperature -- 79 to 80
pH -- 8.0 - 8.2
Alkalinity -- 9 to 10
Ammonia -- Undetectable
Nitrite -- Undetectable
Nitrate -- 5 or lower mostly shows zero with Selfert
Phosphate -- 04 or lower
Calcium -- 400 to 420
Magnesium -- 1350 to 1500

But I am asking about what is attached to paly in the pic. Looks like some sort of pest but I can't identify. Tank is mature, 3 years.

 

[resortez]

Numbers look good. The only thing that I’ve seen that looks in any way similar to that ashy stuff on the mat of the paly, is detritus. Could also be some pests waste. Urchins leave behind similar waste when they poop. Other questions that come to mind is if there is a particular fish that might be picking at them? Hows your water flow? Any new additions to the tank that might have brought in a hitchhiker? Anything has been trimmed or cut off that might have released a substance into the water column? Any changes in your routines? Like adding any new additives or reactors, maybe RO could be contaminated or over spray from cleaning chemicals. Just brainstorming here. The middle of the night when the lights are off is a good time to try to spot any pests feeding on your corals. These are all questions that come to mind when trying to solve that problem. Hopefully it helps & hopefully someone that has experienced this issue can give some input. Good luck.

 

[BeanMachine]

Dip them in a 50/50 mix of hydrogen peroxide and saltwater for a couple of minutes. That looks like algae or detritus, hard to tell.