Estes Spectrastone Lake Green Gravel by Estes $27.15 select a variant 5-lb - $27.15 select a variant 5-lb Title 1 2 3 4 5 6 7 8 9 10+ Quantity Quantity Add to cart Spectrastone lake green gravel is an ideal substrate for fresh water and marine tanks. Our standard colors use silica quartz which is an inert stone that will not affect pH.IngredientsN/A