Help with this algae please

[FloridaGal762]

I have this dark greenish-blackish algae that is on the rock- it doesn't scrape off- it's really embedded in the rock. It seems to have taken over my candy cane coral and is now on my montipora too.

I realized two weeks ago my phosphates had been high and I think this is where the problem started. I added GFO and a filter mat in the filtration and within a week phosphates dropped from 0.9 to 0.07. However, I don't know how to get this coral back to healthy, if I can.

Second issue, my duncan was thriving until the phosphates dropped. Now it looks terrible.

I do tend to get greenish/black algae in the sand bed pretty quickly. I do stir it up and try to vacuum the sand during water changes where I can without damaging the other things in the tank that are around. Not sure if this is related or not.

All water parameters are within a good range. Just now sure off what to do next.
Salinity 34.8
Temp 79.8
Nitrate 5.0 ppm
Nitrite 27 ppb (0.027ppm)
Alk 9.7
Phosphate 0.07
Calcium 478 ppm

Here are photos of the candy cane before and after, the montipora, the rock close up, and the duncan before and after.

 

[lelandmarine]

Does the dark algae disappear at night?

 

[FloridaGal762]

Does the dark algae disappear at night?

No. It’s there all the time.

I almost wonder if I should swap out some of the rock just to help curb the problem. I can’t swap it all out- I have corals attached and growing on some of it.

 

[redeyejedi]

It doesn't look like its the algae thats bugging the coral, probably a water parameter.

 

[FloridaGal762]

It doesn't look like its the algae thats bugging the coral, probably a water parameter.

But the same black is growing all over the base of the corals. That is why I am concerned. Maybe it's not coming from the rock, but it is in the tank. Trying to figure out how to mitigate.

 

[Pkunk35]

Do you have coralline growing? If so, over time I think the coralline will take over.

if bothering frags, I will take frags out and scrape the dark algae off a bit to score it and then drip H202 onto the frag plug directly for 1 min (not onto the coral itself, but you can drip onto the coral skeleton like the non-fleshy bottom of the calustrea). This will usually kill a lot of the algae. You can repeat this process in a couple days to get the plug completely white if it is not already. Also I think the algae is red and the accumulation makes it appear black or dark? Not sure on that one...

Also, IMO i think the declining health of the candy cane and other coral is maybe the GFO dropping phosphate so drastically. I would give it time and stability at the phos level you want for few weeks before changing much else (advice comes from a recent bad experience of mine!). Hopefully they will come back.

I also wanted to mention that their is some correlation between higher/lower nutrient levels and needing higher/lower alk...i've been trying to do some reading recently and this thread has been interesting thus far: https://www.reef2reef.com/threads/light-alkalinity-nutrients.319223/

Hope some of this helps or is interesting!

 

[FloridaGal762]

Do you have coralline growing? If so, over time I think the coralline will take over.

if bothering frags, I will take frags out and scrape the dark algae off a bit to score it and then drip H202 onto the frag plug directly for 1 min (not onto the coral itself, but you can drip onto the coral skeleton like the non-fleshy bottom of the calustrea). This will usually kill a lot of the algae. You can repeat this process in a couple days to get the plug completely white if it is not already. Also I think the algae is red and the accumulation makes it appear black or dark? Not sure on that one...

Also, IMO i think the declining health of the candy cane and other coral is maybe the GFO dropping phosphate so drastically. I would give it time and stability at the phos level you want for few weeks before changing much else (advice comes from a recent bad experience of mine!). Hopefully they will come back.

I also wanted to mention that their is some correlation between higher/lower nutrient levels and needing higher/lower alk...i've been trying to do some reading recently and this thread has been interesting thus far: https://www.reef2reef.com/threads/light-alkalinity-nutrients.319223/

Hope some of this helps or is interesting!

The candy cane coral was declining with the black all over it before the phosphates dropped so fast. However, the duncan head dropped when the phosphates dropped. Will that come back? I thought you wanted phosphates to be close to zero?

The algae can't scrape off- it is embedded in the rock.

What do you think of a black-out or UV light shift? Would that help or hurt? Worried about those corals and I don't want to do more damage!!!

 

[Pkunk35]

The candy cane coral was declining with the black all over it before the phosphates dropped so fast. However, the duncan head dropped when the phosphates dropped. Will that come back? I thought you wanted phosphates to be close to zero?

The algae can't scrape off- it is embedded in the rock.

What do you think of a black-out or UV light shift? Would that help or hurt? Worried about those corals and I don't want to do more damage!!!

Personally, I would not change more than 1 parameter for the few coral declining and I would most 100% NOT change lighting unless you have a very good reason. I see you have a lot of healthy coral in the background, so I would stay stable and see if these few pull through, just my 2 cents, GL!