Black sand

[Capt Crabtabulous]

When I stir up the white sand in my tank the underlying sand is black. It does turn white again eventually (hours). I'm also having a major algae outbreak. Any idea what would turn the sand black?

 

[mcgyvr]

Any smell? Like rotten eggs
Could be hydrogen sulfide..
http://reefkeeping.com/issues/2005-12/rhf/index.php

As to the algae...what are your nitrate and phosphate levels?