Soft vs Hard Water Fish

What Is Water Hardness?

• GH (General Hardness): Calcium and magnesium. Affects fish osmoregulation.
• KH (Carbonate Hardness): Carbonates/bicarbonates. Buffers pH.

Measured in dGH/dKH or ppm (1 dGH ≈ 17.9 ppm).

India Water Hardness Guide

• Mumbai: Soft-moderate (GH 3-8)
• Delhi: Moderate-hard (GH 6-14)
• Bangalore: Soft (GH 2-6)
• Chennai: Very hard (GH 10-20+)

Always test your own water — local variations exist.

Soft Water Species (GH 1-6)

• Cardinal tetras: GH 1-5
• Rummy nose tetras: GH 2-6
• Discus: GH 1-4
• Bettas: GH 3-12 (adaptable)
• Kuhli loaches: GH 1-10
• Corydoras (sterbai, panda): GH 2-12

Hard Water Species (GH 10-20+)

• Livebearers (guppies, mollies, platies): GH 10-25 — they NEED hard water
• African cichlids: GH 10-25+, KH 10-20+
• Danios and barbs: GH 4-16 (adaptable)

Adjusting Hardness

To Soften

• RO water mixed with tap (most reliable)
• Indian almond leaves (mild effect)
• Peat moss in filter
• Driftwood (releases tannins)

To Harden

• Crushed coral in filter/substrate
• Seachem Equilibrium (₹400-700)
• Cuttlebone
• Limestone or Texas holey rock

Pro Tip: Choose fish that match your water rather than fighting your tap chemistry. It makes fish keeping much easier.