Calculate the amount of salt mix needed for your saltwater aquarium. Target specific gravity 1.023-1.025 for marine fish and corals.
Mixing saltwater correctly is fundamental to marine fishkeeping. Using too little salt results in hypo-saline conditions that stress marine organisms, while too much creates hypersalinity that can be equally dangerous. The target specific gravity for most marine aquariums is 1.023 to 1.025, corresponding to a salinity of approximately 34-35 parts per thousand.
Most commercial salt mixes require approximately 1/2 cup of salt per gallon of water, though the exact amount varies by brand. The mixing process involves dissolving salt in RO/DI (reverse osmosis/deionized) water, aerating for 12-24 hours, and verifying specific gravity with a refractometer before adding to the tank.
This calculator estimates the amount of salt mix needed based on the volume of water you're preparing and your target specific gravity. It accounts for brand-typical mixing ratios and helps you batch-prepare water changes efficiently.
Responsible pet owners, breeders, and veterinary professionals benefit from accurate saltwater mix data when making care decisions, budgeting for expenses, or monitoring health benchmarks. Revisit this tool whenever your pet's needs, weight, or age changes to keep recommendations current.
Inconsistent salinity damages corals and stresses marine fish. This calculator ensures you mix the correct amount every time, reducing waste from over-mixing and preventing dangerous salinity fluctuations in your reef or marine fish-only tank. Instant recalculation lets you explore different options and scenarios, ensuring your pet-care decisions are guided by accurate, reliable numbers.
Salt Mix (cups) ≈ Water Volume (gal) × 0.5 cups/gal (at SG 1.025) Salt Mix (grams) ≈ Water Volume (gal) × 135 g/gal Adjust for target SG: For SG 1.023: multiply by 0.96 For SG 1.025: multiply by 1.00 For SG 1.026: multiply by 1.02
Result: 5 cups (1,350 g) of salt mix
For 10 gallons at SG 1.025: 10 × 0.5 cups = 5 cups of salt mix, or approximately 10 × 135 = 1,350 grams. Always verify with a refractometer — brand formulations vary slightly.
Salt mixes vary in trace element composition and are designed for different applications. Reef-specific mixes have elevated calcium, magnesium, and alkalinity for coral growth. Fish-only mixes are simpler and less expensive. Premium mixes dissolve cleaner and produce more stable parameters. Read reviews and match the mix to your tank inhabitants.
Fill a clean container with the required volume of RO/DI water. Add a submersible heater set to your tank temperature and a small powerhead for circulation. Slowly add the measured salt while the powerhead runs. Let the solution mix for 12-24 hours, then test specific gravity, temperature, pH, and alkalinity before use.
Mixing in overly small containers causes super-saturation zones that can precipitate calcium. Not aerating long enough leaves dissolved CO2 elevated, temporarily lowering pH. Adding unmixed saltwater directly to the tank can shock nearby corals. Always premix completely in a separate container.
Fish-only marine tanks can run at SG 1.020-1.023, while reef tanks with corals should maintain SG 1.024-1.026. Most hobbyists target 1.025 for reef systems. Consistency matters more than the exact number.
Approximately 1/2 cup or 135 grams of marine salt mix per gallon of RO/DI water to reach SG 1.025. This varies slightly by brand — always verify with a refractometer before adding to your tank.
Absolutely not. Table salt lacks the essential trace elements, buffers, and minerals that marine organisms require. Always use aquarium-specific marine salt mixes that replicate natural ocean water chemistry.
Mix with a powerhead and heater for at least 12-24 hours. This ensures complete dissolution, temperature matching, and proper pH stabilization. Using freshly mixed water can cause parameter swings.
Tap water contains chlorine, chloramine, phosphates, silicates, and heavy metals that harm marine organisms and fuel nuisance algae. RO/DI water starts pure, so the only minerals in your water come from the carefully formulated salt mix.
A refractometer is the most accurate tool. Place a drop of water on the prism, close the cover, and read the scale. Hydrometers are cheaper but less accurate and prone to air bubble errors. Calibrate either tool with calibration fluid regularly.