Strange color developing one dry rock

[Jetfixr]

Trying to figure out what is going on with my dry rock. Tank started about 4 months ago. Have had a diatom bloom in the past, so I am way past that. Green coloration started on the rocks, but it will not scrub off so it is not GHA. Then recently got this new brownish-tan color starting. Rock started as bone white. It is kinda similar in color to diatoms, but will not blow off with a powerhead nor will it scrub off a brush, scrubbing quite aggressively.

 

[Hoodstream]

I believe that’s the start of Coralline algae. It starts dark green like that and can fade to brown or pink. I have dry rock exactly like that and I had dark green/light green growth and in some spots has actually turned into a purple/pink dots which is Corraline.

 

[Timfish]

+1 You'll also get endolithic algae and other stuff that will burrow into the rocks surface. SInce my inmpression is you're fairly new to reef keeping here's some stuff to look at:

Establishing a Healthy Microbiome in a New Aquarium Using Live Rock

Studying the effects of live rock in a newly established aquarium shows that high-quality live rock promotes the rapid establishment of an effective biological filter and a microbial community similar to those found in mature reef tanks.

www.reef2reef.com

"Coral Reefs in the Microbial Seas" This video compliments Rohwer's book of the same title (Paper back is ~$20, Kindle is ~$10), both deal with the conflicting roles of the different types of DOC in reef ecosystems. While there is overlap bewteen his book and the video both have information not covered by the other and together give a broader view of the complex relationships found in reef ecosystems

Changing Seas - Mysterious Microbes

Nitrogen cycling in hte coral holobiont

BActeria and Sponges

Maintenance of Coral Reef Health (refferences at the end)

Optical Feedback Loop in Colorful Coral Bleaching

Richard Ross What's up with phosphate"

 

[damsels are not mean]

It's hard to tell just by looking what it is specifically, it could be what was said above but it could just be some sort of simple green algae film. In that case most snails will make quick work of it.

 

[Nemo&Friends]

I also think it is the beginning of coraline algae. They vary in color.

 

[Lavey29]

It's probably not coraline algae. Tank is still fairly new. Coraline first shows up on plastic parts like powerheads long before it moves to the rock scape.