Dark patches on acropora

[Henk]

Anyone an idea what these dark patches are?
I first noticed this a few weeks ago , but then the patches seemed smaller. Also appears to have some damaged tips in the dark area.
First photo May 30. Other photos are from today. Thanks

 

[Carabeo]

I'm watching to see more replies. Closest thing I found in the threads was a very similar picture where people responded about patches of concentrated zooxanthellae when there needed to be more light (or new bulbs, I suppose). I hope to hear more soon!

 

[Henk]

I'm watching to see more replies. Closest thing I found in the threads was a very similar picture where people responded about patches of concentrated zooxanthellae when there needed to be more light (or new bulbs, I suppose). I hope to hear more soon!

Thank you for your feedback, and also your mention of patches of concentrated zooxanthellae mentioned in other threads! The acropora is quite high up and under leds (philips coral care). There are some shaded parts that are a bit darker, but the parts pictured from above get direct light from the leds above. So I would be surprised if this is a lighting issue?

 

[sculpin01]

This looks like unhappy coral to me. Possibly bacterial or trace element related.

 

[Henk]

This looks like unhappy coral to me. Possibly bacterial or trace element related.

Latest ICP in June showed no major out of range trace elements, I think, but high level of po4, which I have now been decreasing slowly. That is if test results are accurate. ICP gave 0.18 and Hanna gave 0.2, Red Sea 0.08. Not sure why I often get large deviations between the different tests for Po4. Now according to Hanna at 0.15, Red Sea test gives me +/- 0.06 now. I have added the icp test values maybe you can have a look if anything special needs addressing. Thanks! I have the impression the situation is worsening still .

 

[Rick's Reviews]

Is it only appearing on this coral or others?, Maybe move it away from lights, confused about your readings as you seem to answer yourself....

 

[Henk]

Is it only appearing on this coral or others?, Maybe move it away from lights, confused about your readings as you seem to answer yourself....

Just this one coral. All others doing fine. Even this one is still growing…
I don’t know what my issue is with po4 testing, for other tests - and I test frequently and as accurately as possible - I get results in line with ICP but for po4 Red Sea always gives me results in acceptable range (0.04-0.01, usually 0.06-0.08) whilst Hanna and ICP have given me at times much higher results.

 

[Rick's Reviews]

Just this one coral. All others doing fine. Even this one is still growing…
I don’t know what my issue is with po4 testing, for other tests - and I test frequently and as accurately as possible - I get results in line with ICP but for po4 Red Sea always gives me results in acceptable range (0.04-0.01, usually 0.06-0.08) whilst Hanna and ICP have given me at times much higher results.

Yes unsure about your tests!.

Maybe try moving coral lower from light or even just give it a dip?? I'm sure you got a dip to refresh it?

Your tests results are a different question but for this coral, give it a bath/ dip clean it/

 

[Rick's Reviews]

Yes unsure about your tests!.

Maybe try moving coral lower from light or even just give it a dip?? I'm sure you got a dip to refresh it?

Your tests results are a different question but for this coral, give it a bath/ dip clean it/

Before it effects your other corals

 

[sculpin01]

I personally wouldn't lower your phosphate unless it is climbing. I view 0.05 mg/l as the lowest acceptable aquarium range (also supported by research as below).

In terms of this coral, I'm not sure. It could be something specific to this coral or this could be the "canary in the coal mine" coral, signaling a problem before everything else is affected. Wish I could help more.

Impact of nitrogen (N) and phosphorus (P) enrichment and skewed N:P stoichiometry on the skeletal formation and microstructure of symbiotic reef corals - Coral Reefs

Reported divergent responses of coral growth and skeletal microstructure to the nutrient environment complicate knowledge-based management of water quality in coral reefs. By re-evaluating published results considering the taxonomy of the studied corals and the N:P stoichiometry of their...

link.springer.com

 

[Henk]

I personally wouldn't lower your phosphate unless it is climbing. I view 0.05 mg/l as the lowest acceptable aquarium range (also supported by research as below).

In terms of this coral, I'm not sure. It could be something specific to this coral or this could be the "canary in the coal mine" coral, signaling a problem before everything else is affected. Wish I could help more.

Impact of nitrogen (N) and phosphorus (P) enrichment and skewed N:P stoichiometry on the skeletal formation and microstructure of symbiotic reef corals - Coral Reefs

Reported divergent responses of coral growth and skeletal microstructure to the nutrient environment complicate knowledge-based management of water quality in coral reefs. By re-evaluating published results considering the taxonomy of the studied corals and the N:P stoichiometry of their...

link.springer.com

Thanks for sharing your thoughts. Actually, in hindsight, it seems this issue has manifested itself more prominently after reducing nutrients by increased carbon dosing and lowering phosphates with an iron based liquid phosphate remover. i will hold off a bit on the nutrient reduction and see if things improve.

 

[Brad Mckeon]

Anyone an idea what these dark patches are?
I first noticed this a few weeks ago , but then the patches seemed smaller. Also appears to have some damaged tips in the dark area.
First photo May 30. Other photos are from today. Thanks

This happened to me last week. It showed up on two colonies in a small area when I had a phosphate spike.

 

[thatmanMIKEson]

Thanks for sharing your thoughts. Actually, in hindsight, it seems this issue has manifested itself more prominently after reducing nutrients by increased carbon dosing and lowering phosphates with an iron based liquid phosphate remover. i will hold off a bit on the nutrient reduction and see if things improve.

I've had something similar, I think, when you mentioned carbon dosing, I have no evidence or articles for you but I was dosing a polymer type carbon source at recommend doses but it was hitting or blowing first onto a yellow tips acro I "had" but it was making the skin in that "darker" area puffy almost like water was behind it, or a bilster, I eventually stopped this polymer type carbon source and the puffy skin retracted over a few months, that coral later rtn after looking healthy again, and the entire time during it looked fine even the puffy spots had PE but the polyps weren't long enough to reach through the puffy skin. This could be unrelated?

 

[Henk]

In the end I lost the colony unfortunately, as well as the acropora next to it. Some other colonies showed tissue loss at the bottom. I was dosing quite a lot of carbon, phosphate remained high. Things improved after replacing the sand in the tank which caused nutrients to lower allowing me to drastically reduce the carbon dosage. Tank is running stable again now. I am not sure what exactly happened