Can You Use Gravel in Saltwater?

Saltwater aquariums require different care than freshwater ones. The brightly colored gravel you often see in freshwater aquariums isn't usually suitable for saltwater tanks, but some gravel works well. It's easier to clean than sand but might not provide as much helpful bacteria as live rock, so explore all substrate options to see if gravel is right for your aquarium.

  1. Right Type

    • Many saltwater aquarists use the term "gravel" to describe a tank's substrate, regardless of what the substrate consists of. If you want to use actual gravel as your saltwater substrate, buy the right kind before you get started. Saltwater aquariums rely on the substrate to help create a natural environment in the tank, so stay away from gravel designed for freshwater use. Instead, opt for calcium carbonate gravel. The calcium is a mineral essential to creating the proper environment for your fish.

    Bacteria

    • Part of the substrate's function is to house helpful bacteria. Calcium carbonate gravel allows this bacteria to grow along its many surfaces, helping reduce ammonia buildup from fish waste. This bacteria works in conjunction with filters and bottom-feeder fish to keep your tank clean and healthy for existing fish. You still must vacuum the gravel periodically to remove uneaten food and other waste, so use a gravel vacuum to stir up the gravel and vacuum the particles that rise.

    How Much to Use

    • When adding gravel to your tank, include enough to provide adequate surface area for the bacteria to grow. In tanks with an undergravel filter, 1 pound for each gallon of water typically is sufficient. If you have a 100-gallon tank, for example, you'd need 100 pounds of gravel. With a wet-dry filter that helps support the necessary bacteria, you need about a half-pound for each gallon.

    Other Options

    • Other options besides gravel exist for your saltwater aquarium. Living rock helps you create a reef-type look, while sand reminds you of your last trip to the beach. You can combine substrates, placing living rock in the sand or gravel, for example. Crushed coral typically works well and provides a natural look, as do crushed shells.