Once your tank is set up, it’s time to add water and salt. Prior to adding salt, add a small amount of water to make sure your tank is watertight. Add marine salt until the gravity level reaches 1.021. Use a hydrometer, your tank is ready for a 24- to 48-hour stabilization period and cycling which, when done properly, can take six to eight weeks. To protect your substrate and rock, pour the water into a bowl placed inside the tank, and allow it to overflow the bowl into the aquarium. Remove the bowl. Once you’ve determined the tank is free of leaks, add the remaining water and a water conditioner designed for saltwater tanks.