Aquarium 2-3mm Micro Aqua Gravel - Black & White Mix Fish Tank Substrate
2-3mm Aqua Gravel. As a very rough guide for every 1ft length of Aquarium approx 10Kg of sand or gravel is required. This will give approx depth of 1.5" or 40mm. How Much Gravel Do I Need?. Length x Width divided by 10.