Can you please tell me what this is

[Athalus]

Hi. My new tank seems to be going ok. I have 2 clowns and a bubble tip anemone. This rust colored patch has appeared and over 24 hours is turning up in different spots of the tank.
All parameters are fine and stable.
Can someone please identify it for me and let me know if it is an issue?

 

[cloak]

Diatoms most likely, although Cyanobacteria is a possibility too though.

http://www.reefcleaners.org/nuisance-algae-id-guide

 

[redfishbluefish]

I've never seen it blotchy like that, but google cyanobacteria.

 

[Athalus]

Thanks I googled Cyanobacteria but I am sure it is not that. It doesn't seem to be spreading much. I decided to take a toothbrush to it this morning. Everything seems to have survived that including the Mushroom. So hopefully all good. Doing a water change and bringing down the phosphate so hopefully that will put whatever it is in check.