Unit conversions
Reef aquarium unit conversions
Different test kits, salt mixes, and chemistry articles use different units for the same parameter. Each page below converts one set with the formula, reference table, and a note on which unit to use when.
dKH to meq/L (alkalinity)
Convert between dKH and meq/L for alkalinity. Hobby test kits report dKH; chemistry literature uses meq/L. Same parameter, different scale.
ppt salinity to specific gravity
Convert between parts-per-thousand salinity and specific gravity at 25 °C (refractometer calibration temperature). For aquarium refractometers and hydrometers.
ppm to mg/L (calcium, magnesium, nitrate, phosphate)
ppm and mg/L for aquarium chemistry. The short answer is they're identical in saltwater for practical purposes.
US gallons to liters (aquarium volume)
US gallons to liters for aquarium volume. 1 US gallon = 3.785 L. Imperial gallons differ — make sure you're using US.
°F to °C (aquarium temperature)
Convert reef tank temperature between Fahrenheit and Celsius. Most US reef gear lists Fahrenheit; primary literature and most international gear use Celsius.
mS/cm to ppt salinity (conductivity meters)
Convert conductivity (mS/cm) to salinity (ppt) for digital salinity meters and pinpoint probes. Useful when your meter reads conductivity but your reference is in ppt.
Alkalinity unit converter (dKH ↔ meq/L ↔ ppm CaCO₃)
Convert between the three alkalinity units hobbyists encounter: dKH (German hardness scale), meq/L (chemistry standard), and ppm as CaCO₃ (US drinking-water convention).
Magnesium units in reef chemistry
Magnesium is reported as ppm Mg in almost all reef test kits. If you see other units (mg/L, mmol/L), here's the conversion.
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