Aquarium Salt Mix Calculator — Marine & Freshwater
Calculate marine aquarium salt mix for any tank size, target salinity, and aquarium type (fish-only, reef, brackish, or quarantine).
Aquarium Salt Guide
Marine Salinity Standards
Reef aquariums: 35 ppt (parts per thousand) = specific gravity 1.025 at 25°C. This matches natural ocean water. Coral and invertebrates thrive at this level. Fish-only marine: 30-32 ppt (SG 1.020-1.022). Slightly lower than natural ocean — reduces parasite reproduction rates. Salt cost savings. Hyposalinity treatment: 14 ppt (SG 1.009-1.010). Therapeutic level — eliminates marine ich (Cryptocaryon irritans) without harming fish. Must be maintained for 6-8 weeks minimum. Not suitable with inverte
Mixing Marine Salt Correctly
Use RO/DI water — never tap water. Tap water contains chlorine, copper, nitrates, phosphates. Heat water to 25°C before adding salt. Add salt slowly to water (never water to salt). Mix vigorously with a powerhead or large stir paddle for 12-24 hours. Aerate to drive off CO2 — raises pH. Check salinity after 24 hours with refractometer (NOT a hydrometer — refractometers are far more accurate). Refractometer calibration: zero with RO water, check with calibration fluid (53ppt) periodically. Inaccu
Water Changes
Standard reef tank: 10-20% weekly water change. Removes accumulated nitrates, phosphates, replenishes trace elements depleted by corals. New water must match tank: same salinity, similar temperature (±1°C), pH within 0.2. Premixed water in a separate brute can with powerhead — mix 24 hours before use. Acclimating fish to new salinity: never change more than 0.001 SG per hour. Faster changes cause osmotic shock and fish death. Drip acclimation: tube from tank to bag with airline valve regulated t
Freshwater Salt — Therapeutic
Aquarium salt (sodium chloride only — NOT marine salt) used therapeutically in freshwater. Doses: low dose: 1g/litre. Useful for ich treatment, slime coat support, mild bacterial infections. Most fish tolerate this indefinitely. Medium dose: 2g/litre. More aggressive ich treatment. Many species (livebearers, cichlids) tolerate. Catfish, scaleless species, plants suffer. High dose: 3g/litre. Strong treatment but limited duration (10-14 days). Many sensitive species cannot tolerate. CAUTION: salt
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