Rust Color on Rocks

Can anyone help me identify what/why the color on these two rocks are rust like?
Is that a bad color to have and if so what do I do to correct it?

Thanks!

 

looks like diatoms to me, how old is your tank?

 

Second pic also looks like beginning of hair algae bloom. Keep an eye on it.

 

Looks like diatoms and it also looks like you are at the onset of a cyno bloom as well. Keep an eye on your dissolved nutrient levels.

 

I've had this tank going on 3 weeks now...I bought it from someone and moved it here. He had the tank running for a couple of years. I have been doing water changes almost every 2 days because the nitrates were over 200.

I just tested now and I got the nitrates down to 30....still going to continue with the water changes until I get them down even more.

All the other readings are 0..ammonia, nitrite. Ph is 8.2.

What can I do here to stop this?

 

yes, at 3 weeks you have several months to go and at least 3 more types of algea outbreaks to live thru... welcome to saltwater

 

nothing you can do to stop it, but you can minimize the affects.
what inhabitants do you have?
Are you feeding anything?
Whats your light cycle?

 

I just have 2 gold striped maroon clowns, 1 tang and 1 damsel.
I feed Tues, Thurs, and Sat.
PC Lights are on at 8:00am - 8:00pm
MH lights I just started today at 10:45am - 5:00pm.

Is that light cycle ok? How can I minimize the effects? I will continue my water changes too....