"emorbius" wrote in message ...
A few years ago I bought 400 lbs of a tropical playsand called southdown
at home depot for about $4 for a 50 pound bag. This worked great for my reef
tank because it was argonite based. I wanted to get some more but heard they
are out of business.

Yes, I tried to get couple of bags recently and they are nowhere to be found.

Is there any other sand being used these days that is similiar?

I do not know of any calcium-based sand, but acording to DSB promotor
dr Ron Shimek, any fine sand will do well to be DSB sand, silica sand included.
Sand particles in a reef tank are quickly covered with bacteria film and
they stop acting as a calcium buffer in a pure chemical way pretty soon.
After a while it does not matter what the sand is made of because this
bacteria film is kind of insulating water from chemically reacting with sand.