Aquarium Gravel not only provides aesthetic appeal to your fish tank and a substrate for live plants and aqua scaping, but it also has a number of other benefits. It aids in biological filtration, providing a substrate or "home" for the beneficial bacterial colonies that help keep your fish healthy. A gravel substrate is ideal for bacterial colonies because of its large surface area. In addition, by providing your fish with gravel you are immitating their natural environment which will reduce stress levels in your fish. Stressed fish will often have compromised immune systems and will there for me more susceptible to disease.Aqua One Aquarium Gravel is both practical and decorative. This aquarium safe gravel will add colour and interest to your aquarium, while also providing the perfect surface for beneficial bacteria to grow - helping the health of your aquarium. Available in a range of colours and finishes. Suitable for coldwater and tropical aquariums.