Hugo Kamishi Black glass gravel is a shiny, fine black gravel which would compliment any aquarium. We are asked about the amount of gravel we recommend for fish tanks – this is quite a hard one to answer as it depends on many factors , ie is it a fish or planted aquarium etc . You also need to consider that it is the volume of gravel and not the weight you need to bear in mind i.e some gravels are heavier than others . A normal depth of gravel would be 5cm as an average. Perhaps the most important function that gravel serves is to provide a home for beneficial bacteria. Those bacterial colonies are necessary to eliminate waste produced by the fish, leftover food, and plant debris in the aquarium. If the bacteria don’t have a comfy gravel bed to live in they will find other places, but may not grow in sufficient quantities to keep the aquarium safe for your fish. If the tank is left with a bare bottom, it will be necessary to change the water more often in the aquarium to keep harmful wastes from building up. In the event the tank is heavily stocked, even frequent water changes may not be enough to keep ammonia and nitrites at bay. Occasionally there are situations in which substrate isn’t necessary, or even desirable. The primary one is in a grow-out tank that is used to hatch eggs and raise young fry. Grow out aquariums must be kept scrupulously clean, and require frequent water changes as well as prompt vacuuming away of waste and uneaten foods.