Algae ID - Brown/Black pinhead tufts spreading

[bzb]

Looked on a bunch of the ID guides, can't seem to place this one. This is the same algae that's popping up on my rainbow monti frag. First noticed it last week popping up on the rocks in the center of the DT where the monti is glued. Rocks up high have a little bit, and rocks down low randomly have bits of it.

Little pinhead sized tufts, very dark brown almost black. Just shows up as little speckles on a bunch of the rocks, and seems to be completely random as far as the light exposure.

It doesn't seem to be covering the coralline. I don't notice any of the fish or inverts pecking at it.

90 Gal + 29 sump (~70 gal water)
Tank Age: 6 months
Temp: 78
PH: 7.8
DKH: 8.5
Ca: 440
Nitrate: 0.5ppm
Phos: 0.2ppm

Stock: 8 smaller fish, ~15 blue/red leg hermits, tiger conch, turbo, emerald crab, and dozens of stomatella. Fed approx 1 cube frozen per day (custom BRS-style frozen mix).

Skimmer pulls dry, approx cup per week. 5 gallon weekly water change. Baseball sized chaeto pulled out every 2-3 weeks.

 

[reef lover]

Looks like hair algae to me. Not all is green .

 

[bzb]

Well it's been about a month, and still no clue what this stuff is. My phosphates certainly spiked and no matter what I did, was holding at 0.12ppm, so I've started dosing Phosphate-E.

It's fuzzy and kind of coats surfaces, but seems to trap bubbles. Almost like it may be a dark brown cyano?

I've added a sea hare, handful of new larger snails, and lowered my feeding to try to get the Kole tang or rabbitfish to eat it. A little bit of an impact, but it's just not really going away.

 

[reef lover]

Have you tried vibrant yet? Works well on stubborn algaes.

 

[Sapper Ski]

Sounds more like dinoflagellates to me, but It’s hard to see it in the picture. It’s also consistent with the phosphate increase (happened to me as well only mine spiked to .6). Vibrant worked in my case.