Alkalinity

Water's capacity to neutralize acid. Reported as dKH, meq/L, or ppm CaCO₃.

Alkalinity is the most-tested parameter in reef chemistry because coral calcification consumes it. Target: 7–9 dKH for most reefs (SPS-dominant, low-nutrient systems often 7–8), or 8–11 dKH if you run the elevated band some salt makers recommend. Natural seawater is ~6.5–7 dKH.

Last reviewed 2026-09-30