Water Parameter Balancing: GH, KH, pH & TDS Explained

Understanding and controlling GH, KH, pH, and TDS lets you customize conditions for fish, shrimp, and plants. Stability matters more than chasing one "perfect" number.

Key Definitions

Parameter What It Measures Importance
GH Calcium & magnesium ions Osmoregulation, shell/exoskeleton health
KH Carbonate/bicarbonate buffering pH stability, CO2 interaction
pH Acidity/alkalinity Species comfort, biological processes
TDS Total dissolved solids Overall mineral concentration proxy

Target Ranges (Typical Community Tank)

Parameter Range
GH 6–10 dGH
KH 3–6 dKH
pH 6.6–7.6
TDS 180–260 ppm

Adjust for specialized species (e.g., Caridina shrimp prefer lower GH/TDS; African cichlids higher).

Testing Routine

  • Weekly: GH, KH, pH
  • Monthly: TDS baseline
  • After major changes: Re-test all within 24 hours

Adjusting GH

  • Raise: Mineral salts (CaSO4, MgSO4), commercial remineralizers
  • Lower: Dilute with RO/DI water (do not use distilled alone long term)

Adjusting KH

  • Raise: Baking soda (sodium bicarbonate) cautiously; commercial buffers
  • Lower: RO/DI dilution; peat (light effect + tannins)

pH Influence Factors

  • CO2 injection lowers pH temporarily during photoperiod
  • KH acts as a brake against rapid pH swings
  • Organics (wood, botanicals) gently soften & acidify

Recognizing Instability

Symptom Possible Cause Correction
Fish gasping mornings CO2 spike / low O2 Increase surface agitation at night
pH swings >0.5 daily Low KH Raise KH gradually (1 dKH increments)
Failed shrimp molts Mineral deficiency Raise GH with balanced remineralizer

Building a Remineralization Routine

  1. Start with RO/DI base
  2. Add GH/KH salts to target ranges
  3. Log amounts per gallon for repeatability
  4. Match new water parameters before each change

Final Thoughts

Parameter management is pattern recognition. Test, log, adjust slowly—your livestock thrives under steady, predictable chemistry.