BLACK GLASS AQUARIUM SAND with Orange SPARKLES - pack- 5kg Gives a shine when the light hits it in tank. The sand is 1-1.5mm in size making it suitable for any tropical or coldwater aquarium. Ideal for catfish, eels etc and for growing plants. With 6mm Blue gravel added to give a sparkle. Inert - will not alter the aquarium pH. As a guide 10kg will give a good base layer for a square foot of aquarium base size, so this 5kg bag will do a 18" x 12" aquarium to about 1" deep or a larger tank on a thinner layer. Prewashed but if not rinsed dust may appear on the aquarium water surface - this is not harmfull and will disappear with you filter in an hour or two. We use this sand in tanks without washing and the water soon clears. Or if unsure rinse with clean water. Upon arrival this sand /gravel may have settled - just mix before adding to the aquarium. Comprises 80% sand 20% gravel