Fuzzy algae ID

[Wiinberg]

Hi.

My tank has been running for 2 months now, and most of the normal algae is gone. What's left is a blanket of colorless fuzzy something. I've scrubbed the rocks in tank water, but within a week, it's back.

Nitrate: 0
Po4: 0,02-0,04
RO/DI

I have turbo snails and a tuxedo urchin, and a yellow tang, but they don't seem to touch it.
Plenty of flow, and pretty normal light cycle.
The fuzzy thing only seems to grow on the part of the rocks that are being hit with direct light though.

 

 

 

 

I'm thinking chrysophytes, so i've just replaced my DI resin and membrane in the RO/DI filter.

If you guys have any idea what it is, or what to do, it would be very helpful.