Non-buffering Sand...

[justinl]

the use of black sand is very much like using a BB. only difference is that detritus will show up more and bacteria will have surface area to grow on.

buffering would not be a large concern imo unless you're adding weird stuff (which under normal circumstances you wouldnt be).

[michika]

I use blacksand with no noticable effect on my pH or any other parameters in my tank. It also looks pretty cool, and doesn't show the detritus as much in any dead areas.