Ok I believe I voted 2" but can't remember lol but anyhow it ranges from 1"-4" due to my mp60 and my stingray putting it were he thinks it should go. But as for the brown algae don't really have a big problem with it I have a couple hundred snails and hermit crabs and a huge sand sifting starfish so with all of them put together my sand is turned constantly. And as for the debris floating in my tank when it's disturbed I don't really have that problem anymore. The first couple months I had my tank I had it horrible couldn't really figure out what it was but it was from my stingray constantly burrying himself in the sand and coming out and shaking it off on top of him always sucking up the sand and flushing it out the holes on top of his head looking for inverts. It was a thorn in my side for a couple months but I'm glad cause now I can run my hand through the sand and nothing it all settles immediately but that's just me.