Salt Mix Calculator
Estimate how much marine salt mix you need for a water change or a new batch of saltwater. Always mix to a refractometer reading — brands vary slightly.
Frequently Asked Questions
How much salt do I need per gallon?
As a rule of thumb, roughly half a pound (about ½ cup) of reef salt mix per US gallon reaches a reef salinity near 1.025 specific gravity (~35 ppt). Exact ratios vary by brand, so always confirm with a refractometer.
What salinity should a reef tank be?
Most reef tanks are kept at 1.025–1.026 specific gravity (about 35 ppt). Fish-only tanks can run a little lower. Match your water-change water to your display salinity.