Brown spots in sand.

[yraen]

Not sure if this is the right section for this! Sorry if it's not!
I did a search about this and came up with something about diatom. Sorry if this is a stupid question, just worried. I had a 12 nano set up with live rocks and live sand. It an unused bedroom for about 2 years with the pump/filter on. After sick of seeing an perfectly usable aquarium with only sand and rocks in it, I decided to go to my local saltwater aquarium store for information. I took them a sample of the water and they tested it and said it would be fine for a fish. I got a yellow/purple Gramma and I've been feeding it 1/4 cube of frozen brine everyday (too much? too often?). Everything seemed to be going fine. I noticed a bit of green algea growing on the rocks, so I got about 6 snails and they cleaned it all up.
Today I came back from work and noticed that there were some brown spots in the sand. There have been some before, but not this many. Obviously, I got worried and did a forum search here. I'm new to this and was just wondering what it is, should I be worried and what should I do?
Full tank view (gramma is hiding as usual)

Should I be worried? =(

Thank you in advance! I really hope someone can tell me if I need to take action.

 

[paintballer768]

Looks like diatom algae. No need to worry. Is the tank still cycling?
PS if its been sitting empty for 2 years, make sure the silicon lining didnt dry rot.

 

[yraen]

Thanks for the info. Well, while the tank was sitting, it had water, live sand and live rock in it. The water was at a constant 78 degrees and went through the filters/pump during the time it sat there. I've had the gramma in for about 10 days, snails have been in for about 4 days.

 

[paintballer768]

Oh ok, then no need to worry about the silicon. It should have been cycled if it had all that for that period of time. Diatoms require silicates to exist and form their cellular structure, so this is probably a slight diatom bloom, due to the new introduction of food and waste. It will clear itself up. I would recommend getting some nassarius (sp?) snails for sand cleaners, and some astrea for the glass. Once you have those snails and a few hermits, youre clean up crew will be set and you shouldnt need to worry about much algae after, except for cyano if it shows up. Cyano is a different story, but for now keep everything up like normal and see how it goes.

 

[yraen]

Awesome, thank you so much for the information! <3

 

[perfectdark]

What type of substrate is that?

 

[yraen]

It's live sand purchased from this site. I do have another question. On one of my rocks (figi rocks from this site), I have noticed small little red hairs growing. Do you guys know what this is?
Here's a pic, blurry and very hard to make out, but 2 little clusters of these hairs have started growing on one of the rocks.

 

[paintballer768]

Its nearly impossible to tell what the red hairs are, but Im willing to guess some type of algae. Your clean up crew should get it, but try to get a better picture and we'll see for sure.

 

[yraen]

Alright, I'll stop by the aquarium store today and try to get a better picture tonight. Thanks again for all the help!