Planted Tank Enthusiast
Join Date: Apr 2012
Location: Edmonton, Canada
That bag of black substrate is a good option especially if you don't want a big bag. I've used ExoTerra black sand in a tank as well. Comes in about the same size bag.
Alternatively... Sil industries or Burnco should have black beauty or something similar, although you'll be getting that in much larger quantities, but cheaper than that little bag.