How much
How much salt for a 120 gallon?
Pre-calculated for the 120 gallon (48 × 24 × 24 in · raw volume ≈ 120 US gal · water volume ≈ 108 US gal).
By scenario
| Scenario | Amount |
|---|---|
| Initial fill (cycling the tank) | 35.6 lb (16145 g) Or about 1.96 × 7 kg buckets / 0.62 × 22 kg buckets. |
| 10% weekly water change | 3.57 lb (1620 g) 10.8 gal new saltwater. Many reefers settle here as a routine. |
| 20% bi-weekly water change | 7.14 lb (3240 g) 21.6 gal new saltwater every 2 weeks. |
| Annual salt budget (10% weekly) | 186 lb (84.2 kg) Plan on 13 × 7 kg buckets per year. |
Brands hobbyists actually use
Buckets reefers actually buy at this volume. Coral Pro for high-alk SPS, Pro Reef for low-alk dosing tanks, Reef Crystals for budget mixed reefs.
Red Sea Coral Pro Salt — 22 kg bucket (175 gal mix)
Best per-gallon value for SPS tanks.
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Tropic Marin Pro Reef Salt
7–8 dKH spec. The go-to for calcium-reactor and Triton tanks.
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Instant Ocean Reef Crystals — 200 gal box
Cheapest reef salt with decent reef chemistry. Used to start.
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