Unipac Silica Sand is a ph neutral sand that wont affect the water chemistry of your aquarium. Silica Sand can be used to create a natural and realistic underwater world, that is especially suited to plants. This sand looks stunning when used as the base substrate of any freshwater aquarium. Silica Sand is inert, meaning it will not adversely affect the pH or water chemistry of your aquarium and it has been pre-washed to remove any unwanted contaminants.