Aquarium Salt Mix Calculator

A common reference is about 127 grams of marine salt per US gallon to reach roughly 1.025 specific gravity. So 30 gallons needs about 3810 grams, or 3.81 kg. The exact amount depends on your brand, so use this as a starting point and confirm by measuring.

Many reef keepers target about 1.025, while fish only systems often run a little lower around 1.020 to 1.023. This tool scales the salt dose linearly from pure water, so a 1.020 target needs about 80 percent of the salt that 1.025 does.

Different marine salt brands have slightly different mixing rates. If your bag says a certain amount makes 1.025 specific gravity in a gallon, enter that figure so the result matches your salt rather than a generic average.

Use a calibrated refractometer or a quality hydrometer, and check at a consistent temperature since salinity readings shift with temperature. Mix, aerate and let the batch dissolve fully before you measure and fine-tune toward your target.

It is approximate and brand dependent. Real salt amounts vary by mix formula, temperature and how you measure, and the linear scaling is a simplification. Always confirm with a refractometer and adjust the salt before adding livestock.