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How to choose
Salt sets your baseline for alkalinity, calcium and magnesium with every water change. Pick one that matches your tank's target alkalinity so water changes don't cause swings. Stick with it, since switching brands shifts your parameters. Elevated-parameter salts must be mixed and used as directed to avoid precipitation.
- Match salt alkalinity to your tank. If you keep 8 dKH, a 12 dKH salt will bump it at every change.
- Mix with RO/DI water to your target salinity, and verify with a calibrated refractometer.
- Heat and circulate stored saltwater, and follow the label's maximum mixing time for elevated salts.
For the science behind it, read our Salinity and RO/DI guide.
How we review: we paraphrase what owners report in retailer reviews and forum threads, plus picks and test results from BRStv, Reef2Reef discussions and published reef chemists. We only show a rating when we verified it at the source, with the date we checked. We don't invent scores or quotes. Prices and stock change, so check the retailer.
Well-regarded picks
Tropic Marin Pro-Reef Salt
Pharmaceutical-grade salt (about 7–8 dKH)
- What reviews say: strengths
- It mixes fast and clear with little residue, and keeps lower, natural-seawater-like alkalinity.
- Weaknesses
- It costs more per bucket than most mass-market salts.
- Who it's for
- SPS and mixed reefs that keep alkalinity near natural seawater, and anyone storing mixed water.
- Expert consensus
- In BRStv Investigates tests, Tropic Marin Pro mixed clear fastest and stayed stable in storage. BRS's 2019 roundup says it scored at the top for mix time, impurities and consistency. In BRS's interview, Tropic Marin's Lou Ekus says Pro-Reef mixes to about 7–8 dKH.
Sources
Where to buy:
Red Sea Coral Pro Salt
Elevated-parameter salt
- What reviews say: strengths
- Elevated calcium, alkalinity and magnesium for fast-growing coral tanks. BRS says it's tied for its best-selling salt.
- Weaknesses
- High alkalinity (about 12 dKH in BRS's test) can bump a lower-alk tank, and it showed the most precipitation and drift when stored.
- Who it's for
- Coral-heavy tanks that already run higher alkalinity, and reefers who mix and use water the same day.
- Expert consensus
- BRStv Investigates found Coral Pro the outlier in unheated storage, with the biggest calcium and alkalinity changes. BRS notes that Red Sea tells users to mix for about 2 hours (no more than 4), heat, then use it.
Sources
Where to buy:
Instant Ocean Reef Crystals
Reef salt with extra calcium
- What reviews say: strengths
- It's affordable and widely available. Alkalinity held steady in BRS's two-week heated storage test.
- Weaknesses
- It mixes to fairly high calcium and alkalinity (roughly 490–500 ppm and 10.8 dKH in BRS's test), which may not match your tank.
- Who it's for
- Budget-minded reefers and those who buy salt locally.
- Expert consensus
- It was among the eight popular salts BRStv Investigates tracked through storage, where it showed no alkalinity change over two weeks in heated, circulated storage.
Sources
Where to buy:
Fritz Pro Reef Mix (RPM)
Reef salt
- What reviews say: strengths
- It's a reef-specific salt from a long-standing US maker.
- Weaknesses
- It wasn't part of BRS's eight-salt storage tests, so we have no independent mix or storage data to share.
- Who it's for
- Reefers who prefer a US-made salt. Verify its alkalinity against your target.
- Expert consensus
- We couldn't find a verified expert test of Fritz RPM, so we don't make performance claims about it.
No independent expert source verified. Summary based on retailer and manufacturer information.
Where to buy:
Spot an error or a product we should add? Specs and availability change often, so always check the manufacturer's current listing.