New 🐟 Mercury Safety Guide & Omega-3 Rankings Updated for 2026. View Omega-3 Rankings →

🧊
Mineral Chemistry

GH (General Hardness)

A measure of dissolved calcium and magnesium in water - essential minerals for fish osmoregulation, shrimp molting, and plant nutrition.

Unit: dGH Code: GH

📊 Ideal Ranges

Freshwater
4-12 dGH
Planted
4-8 dGH

📖 Overview

GH is measured in dGH (degrees of general hardness) or ppm as CaCO3. Fish from soft water (Amazon tetras, discus, Apistogramma) thrive in 4-8 dGH. Fish from hard water (livebearers, African cichlids) prefer 12-20 dGH. Shrimp molt properly only in adequate GH.

📈 How to Raise

GH booster (Salty Shrimp, Seachem Equilibrium). Crushed coral. Limestone. Seiryu stone. Calcium chloride.

📉 How to Lower

Reverse osmosis water dilution. Peat moss (softens over time). Distilled water. Rainwater (with caution).