crushed marble vs. silica sand for DSB

[RustySnail]

I would expect aragonite sand to be more soluble than sand made of marble (dissolves in seawater less than ~400 feet deep). Bond geometry in mineral solids make quite a bit of difference in their ability to dissolve. But if calcium dissolution that is not that important to you, then go with the marble sand. Should be fine, better choice than silica sand IMHO. I'm using a 50/50 mix of southdown and dolomite sand (Mg(CO3)2). You can get dolomite sand at some sand/gravel distributors that sell swimming pool sand. It's ultra-white. Makes a nice mix with southdown.

The warning on the bags of silica sand are mostly due to the use in sandblasting. The silica sand gets pulverized to dust and can lead to silicosis if you breathe the dust all the time. Makes parents worry too when their kid is playing in silica sand. (hence the need for southdown 'tropical playsand')

 

[Anonymous]

I used dolomite in my last tank too, worked pretty well

 

[mikenegue]

Based on many of your comments, I've decided to use both types of sand available to me here at the local Southern California Home Depot: crushed marble and silica-based sand. I have kept the two types of sand separate, laying down the brown silica sand in the inner portion of the tank and lining the glass-front/sides with the white crushed marble. I am also putting a layer of the white crushed marble on top to create a consistent coloring.

I am trying to hedge my losses on this one, by getting both the benefits and shortcomings of each type of sand. They were about the same price, under $5 for 50 lbs. I am going to seed it with some live sand that one of you has graciously offered me (if anyone else has a cup of sand, I'd be grateful for it).

I'm also laying some rock on top of the sand: flat limestone as a base, some dead ocean rock, and then a few pieces of live rock on top. Will this do? Or should I place the live rock directly on the sand to help seed the sand... and then after a few weeks re-do the rocks in the manner mentioned above?

By the way, thanks for all the helpful advice about the sand. With a tight budget, I went for diversification and aesthetics, and I think that I'll do ok. Oh, the sand bed is around 5 inches deep... is that deep enough?