What is this thick, purple algae that has suddenly taken over the rocks in my 4 month old reef tank?

[gareefer1029]

Pictures and a video attached. In some places the algae has hair-like extensions.

Tank is a 29g, with x4 corals, 1 urchin, a bunch of crabs/snails, and 1 fish (a blue/green chromis).

Levels are generally good:
-PH is around 8.1
-Ammonia is 0
-Nitrites are 0
-Nitrates are 10
-Temp is 79
-I don't really test Phosphate, Calcium, etc. I just add Reef Fusion 1 and Reef Fusion 2 supplements every other day

How do I get rid of this algae??

 

[Jeto2004]

Looks like cyano bacteria to me. Knowing your phosphate would be helpful. There a plenty of threads on R2R that talk about how to get rid of cyano - as with anything reefing there is not one way to get to your desired result.

 

[vlangel]

I can not tell from your pics but there is a photosynthetic purple sponge that spread fairly quickly.

 

[Biglew11]

+1 looks like cyano.
Reef fusion 1 and two is for calcium and alkalinity if your dosing it you need to test it. Do you have any corals that are using calcium and alkalinity? Also snails and other creatures that make their own shell also use it.

 

[Rhoads238]

I agree that it looks like cyano. It can be a pain to get rid of. It’s very common in a new aquarium. I’m sure there are loads of threads here about how to deal with it.

Cyano is photosynthetic, what I have done in the past was a three day blackout. Combined with manual removal before the blackout and a large water change after. Most likely if you test for phosphate, you will get a low or zero reading. This is because the bacteria consumes phosphate.