What is growing in my aquarium?

[Kimberly Colwell]

I am new to the saltwater Hobby and got my tank set up weeks ago beginning with live sand only. A week or so after I added live rock and 5 snails and 5 small hermit crabs . Then a bit later added 2 fish. Then the next day I notice these brown dots everywhere in the sand. They are spreading like crazy and it's everywhere. I even noticed it on my magnetic glass cleaner.
How do I get rid of this stuff without harming my fish and before it causes damage to my rock? Help!

 

[Big G]

Diatoms. Check this video.

 

[Broadfield]

Yep, it's diatoms that are a natural part of a new reef tank. Diatoms feed on silicates... which sand has a lot of. As long as you are doing water changes and top offs with 0 TDS RO/DI water, then there will be no additional silicates added to the tank. Once the silicates are exhausted, then the diatoms will go away as quick as they appeared. Diatoms are not harmful to your tank inhabitants.

 

[Kimberly Colwell]

Thank you! The tank is due for water change in the next few days.