Help: SPS peeling strangely.

[Kruss7]

Hi everyone,

I'm experiencing some issues with my Acropora frags and mini colonies, and I'm hoping to get some advice. Some of my SPS corals are showing signs of peeling and STN, and it's quite concerning. (This is happening slowly, losing an acro every few days not rapidly). Most of my acros look absolutely amazing but this seems like it’s going from one to another.

Parameters:
Temperature: 77.5-78.5°F
Salinity: 1.026 (35 ppm)
Alkalinity: 8.4 dKH
Calcium: 470 ppm
Magnesium: 1410 ppm
Phosphate: 0.08 ppm
Nitrate: 20 ppm

About a month ago, I experienced an alkalinity swing. It wasn't fast or super significant; it slowly dropped to around 6.5 dKH over a week and then gradually increased back to 8.5 dKH the following week. I'm not sure if this could be the cause, but it's a possibility. I'm am also currently waiting on ICP results, which should be available soon.

Interestingly, some of the SPS corals that have died were peeling with their polyps still extended. The peeling is strange as it isn't starting from the bottom up; spots on the branches are peeling first. I've dipped them and haven't found any pests, and there are no bite marks or eggs present. I had AEFW a long time ago, but haven't seen any since then and this isn’t looking like that did.

Could this be a bacterial infection? Any insights or suggestions would be greatly appreciated. I'm at a loss and want to save my remaining corals.

Thanks in advance for your help!

 

[griss]

IME, this has always been difficult to diagnose as there are many things that can cause something similar. I've had it happen several times over the years and, sometimes, I was never able to identify or treat the cause.

Given that you aren't seeing any AEFWs and have experience with them, we can (as you stated) likely rule those out.

What about Red Bugs of White Bugs? Have you looked at the Acros under magnification? These Bugs (if you don't have any experience with them) can be difficult to see with the naked eye.

If that's not the case, it could have been the Alk swing but, I've had some in the past that were the same magnitude and didn't have any issues so, I don't think that is the case.

A couple observations:
1. Temperature is good.
2. Salinity is good.
3. Your Ca is slightly high which could suppress Alk.
3a. But, with your Alk in the acceptable range (although the lower end) I think you're okay there.
4. You Mg is just a tiny bit high so, I don't think that's the issue.
5. Your PO4 is in the higher range of, "Tolerable" so this could be part of the problem.
6. Your NO3 is also in the higher range of, "Tolerable" and, again, could be part of the problem.

What is your pH?

What dip did you use to try to treat them?

I would see about slowly lowering your PO4 and NO3 first and also posts the results of the ICP test once received.

Also, check any magnets in the tank for signs of rusting. Things like powerhead magnet mounts, algae scrapers, etc.

Also, if you have glass heaters, check those for cracks/breakage.

It's possible it's a bacterial infection. But, without knowing what bacteria is it, it could be hard to treat. An iodine/Lugol's dip may help.

Another, more drastic action, if fragging the affected frags/corals. Frag them well away from the affected area and remount the healthy portions.