How to kill this brown stuff?

[Liron Mishal]

Hi
Fairly new tank, 100g, running for about four months.
This brown stuff grows on some of my rocks, scubbing it doesn't work as it grows back the day after.
It prevents the xenia coral from pulsing, and can also be seen on the sand bed.

Tank cycled with dry rocks and sand.
Currently in the tank:
Yellow, purple, blue and scopas tangs,
Small percula and firefish.
Cleanup crew is 2 fire shrimp, a lismata shrimp, 1 turbo and 6 nazarius snails.

Phosphate reads .3 (salifert)
Nitrate is at 5 (api). Chinese black box for lighting.

Any ideas?

 

[Halal Hotdog]

.3ppm phosphates is pretty high. Beyond that a picture would absolutely help identify what type of algae you have.

 

[Liron Mishal]

Pictures added

 

[Liron Mishal]

Forgot to add, using rodi water, tds is 0.
Red sea coral pro salt.

 

[monkeyCmonkeyDo]

that's a lot of tangs! Tangs like to eat, swim, and poop a lot...as do most fish! anyways.
Id let it be and do ur wcs or turn ur skimmer up a lil... u can run carbon maybe too. Looks like diatom to me.
Could be dinoflagellates I guess if it gets stringy or bubbly. HTHs
-d

 

[monkeyCmonkeyDo]

don't mess with it too much or try and remove it. U would be just spreading it... Do a wc after if ur gonna b aggressive with it like that.
-d

 

[Liron Mishal]

If it is dinos, will it go away by itself? Or is it here to stay?

 

[monkeyCmonkeyDo]

dinos need to be tackled and attacked the aggressive way. Carbon. Chemi pure elite. WC's. Bigger the better. skimmer up the volume output. dinos may go away on their own but will take a long time if u just stick to ur reg routine.
diatom is a come and go cycle algae. dinos another animal. Dino will be stringy and bubbly! It will rise up off ur rockwork or whatever and the bubbles will hold it up in the water column. Ill try and get pixs of the two diffrences on here for ya!
-d

 

[monkeyCmonkeyDo]

small picture but initial diatom bloom may look like this. Better with tank lights off. for cycling. dark. ect.

 

[monkeyCmonkeyDo]

these would b dinoflagellates! With some cyanobacteria probably.

 

[monkeyCmonkeyDo]

Ive had it in big long strings like 8-10" long.
-d

 

[Liron Mishal]

Thanks, but it looks a little bit of the two pics...
it is stringy but i dont think it bubbles like at the pic above, perhaps some air trapped in it from the water column, but it is definitely stringy.
is there a guide of how to id it under a microscope somewhere?

 

[monkeyCmonkeyDo]

Idk. U might be able to google img microscopic.scientific views...
D