Potassium Supplement Calculator
Calculate the exact amount of dry salt needed to raise potassium in a reef aquarium. Target is typically ~380–410 ppm (NSW ≈ 400 ppm).
Tank & Levels
Increase needed
50 ppm
Amount of salt to add
— g
Approx. teaspoons (level)
—
How to dose: Weigh the calculated amount carefully. Dissolve in 0.5–1 L of RO/DI water until clear, then drip slowly over several hours into a high-flow area (sump return, weir, etc.). Do not raise more than 5–10 ppm per day.
Important Notes
- Natural seawater potassium is approximately 380–410 ppm. Most reef keepers aim for ~400 ppm.
- Potassium is only slowly consumed. Large daily doses are rarely needed after the initial correction.
- KCl is the preferred and most commonly used salt. Food-grade potassium chloride (sold as salt substitute) is suitable if free of anti-caking agents.
- Potassium test kits can be difficult to read accurately. ICP analysis is the gold standard. Always verify your test kit against a reference solution when possible.
- Excess potassium (>450–500 ppm) has been linked to algae issues and stress in some SPS corals. Raise gradually and re-test.
- Do not perform other major chemical adjustments (Ca, Alk, Mg) at the same time as a large potassium correction.