Estes Marine Sand: suitable for Fresh & Saltwater Environments, non-toxic & colorfast. Our pH neutral, high grade silica sand is a consumer favorite. Estes has a long history in the aquarium sand industry - we pioneered colored aquarium sand. Our understanding of the chemistry of our products and its impact on aquatic life is unparalleled. With extended selection of marine sand colors and premium quality you can rely on, Estes is the trusted choice.