Dark / Grey spots on Acropora?

TomSerious · Aug 30, 2021

Hello!
So one of my Acropora (SSC), I received with a greyish colored spot and thought it would go away in a few months when it settled in.

Now it's been a few months and it has grown in, but the grey spot has grown with it ...

Does anyone know what this could be?
Is this a permanent thing?
Should I cut it back so that the grey area is gone?

Last ICP showed a little bit of aluminum and my Iodine was too low.

Thank you in advance!

This is it today:

This is it about 8 months ago:

Timfish · Aug 31, 2021

Looks like reduced protein production in that area due to low light. Many corals as they grow will show some kind of variation in color due to the amount of light the surface of the coral is actually recieving, or not receiving. Areas that are partially shaded may have very little color, may be white and sometimes lack of light around teh base of fingers and colonies will cause localized dieoff of the polyps. Personally I would not change a thing if that coral was in one of my tanks. Trying to change lighting to get the gray areas to color up is going to cause everything else to alter their photobiology and unless you're experienced with how every coral reacts to different light levels and spectrums you're shooting in the dark and may cause more problems.

homer1475 · Aug 31, 2021

Basically what he's saying, the grey is caused by shading. You can see it in the mini colony shot on some of the branches that are toward the inner part of the colony. Trying to fix it, may hurt the coral more then just looking at the shaded spot.

TomSerious · Aug 31, 2021

Timfish said:
Looks like reduced protein production in that area due to low light. Many corals as they grow will show some kind of variation in color due to the amount of light the surface of the coral is actually recieving, or not receiving. Areas that are partially shaded may have very little color, may be white and sometimes lack of light around teh base of fingers and colonies will cause localized dieoff of the polyps. Personally I would not change a thing if that coral was in one of my tanks. Trying to change lighting to get the gray areas to color up is going to cause everything else to alter their photobiology and unless you're experienced with how every coral reacts to different light levels and spectrums you're shooting in the dark and may cause more problems.

Thank you for the great information!

homer1475 said:
Basically what he's saying, the grey is caused by shading. You can see it in the mini colony shot on some of the branches that are toward the inner part of the colony. Trying to fix it, may hurt the coral more then just looking at the shaded spot.

Thanks!

lemonade · Aug 31, 2021

Looks almost like some grafting going on or it has some genetic mutation. I don't think its a lighting issue, imo. It looks well lit, if it were from shading it would be more uniform and all branches would show signs not just that section.