How to Replace Sandbeds in Aquariums

Aquarium substrate is the solid, granulated material that lies at the bottom of the tank. Sand is one of the most widely used substrates in domestic aquariums, but gravel, aragonite and crushed coral are common alternatives that provide different aesthetic and habitat qualities. Changing the sand in an aquarium can be a laborious process that is stressful on the fish and other organisms in the tank.

  1. Amount

    • To calculate the amount of sand you need to replace your aquarium's current substrate, simply multiply the length of the tank by its width, then multiply the result by the height of the desired sand bed. The product of these three dimensions gives you the volume of sand required. Divide the volume by 20 to estimate the amount of sand needed in pounds, according to Algone. Most tanks only need a substrate depth of 1 to 3 inches, but larger or specialty tanks may have different requirements.

    Secondary Tank

    • Fish and other organisms should be removed from the aquarium before replacing the sand. Attempting to remove the sand while the fish are in the tank can send them in to shock or they may be physically hurt by accident. The sand will also cloud the water and may suffocate some species. Prepare a secondary tank by filling it with water from the original. You can also prepare a secondary tank by adjusting the water to the original's pH and nutrient levels, but don't simply fill a tank with tap water, as it may contain harmful chemicals.

    Drain and Clean the Aquarium

    • Drain the water from the aquarium into a storage tank or sump pump. If neither of these options are available, remove the water by dipping a container into it and emptying it into a drain. Repeat this process until you are able to safely lift or tilt the tank enough to drain the remaining water. Remove plants, rocks and other decorative material before completely draining the tank. Empty the current substrate and rinse the aquarium with clean water. Don't use soap or chemicals to clean the tank unless the product is specifically designed for aquariums. Residue from cleaning solutions can linger on the walls and poison the fish once they are back in the tank.

    Re-establish the Aquarium

    • Measure out the amount of sand you need to fill the tank up to the desired depth. Pour the sand in slowly and give it a few minutes to settle before adding water to the tank. Replace the filter and adjust other automated devices as needed before filling it with water. After the tank is filled, allow the systems to run until the chemical balance and water temperature are at normal levels. Put the fish back in the tank and watch them closely over the next several hours. If they exhibit signs of distress, remove them immediately and put them back into the secondary tank until you can identify the problem.