dKH

Definition

dKH (degrees of Carbonate Hardness) measures the buffering capacity (alkalinity) of aquarium water, specifically the bicarbonate + carbonate concentration. Higher dKH = more resistance to pH swings.

Practical use in aquariums

Reef tanks target 8-12 dKH (most stable at 8-9 dKH). Freshwater planted tanks run 3-8 dKH typically. Test with a Salifert or Hanna alk checker; swings of more than 1 dKH per 24 hours stress coral.

How dKH fits the bigger picture

Understanding dKH matters because it's connected to broader husbandry decisions: water chemistry is the foundation of every other aquarium parameter - chemistry mistakes show up months later as livestock loss.

Browse the Fast Aquatics care library for full husbandry tutorials covering dKH in context.