This combination of black and white sand is a wonderful addition to your terrarium.It can create dramatic, contrasting layers that give your ecosystem a pop.Sand serves first as an additional drainage medium, though can also be used to create decorative layers - or even a top-layer beach! White sand in particular helps brighten your terrarium, while black can be used underneath as a barrier between the soil and white sand.Sand can also be used generally as an addition to cacti and succulent substrates.In your order you will get an equal quantity of both white and black sand.