Conversion

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.

Formula

mg/L  ≈  ppm
ppm  ≈  mg/L

Quick reference

ppmmg/L
5050
100100
200200
420420
13001300

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