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How to choose
Testing is how you know what to dose. For most reefers, alkalinity is the parameter to test most often, followed by nitrate and phosphate, then calcium and magnesium. The big trade-off is precision and convenience (digital checkers) against cost per test and simplicity (titration kits). Experienced reefers stress that a consistent test you use often beats a perfect one you skip.
- Test alkalinity at the same time of day, since it swings between lights-on and lights-off.
- Cross-check any kit against a second brand or an ICP lab test now and then.
- Keep cuvettes and syringes clean, and replace reagents before they expire.
For the science behind it, read our Alkalinity, calcium and magnesium 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
Hanna HI772 Marine Alkalinity Checker (dKH)
Digital colorimeter
- What reviews say: strengths
- Reviewers like that it gives a number instead of a color match, takes about a minute, and repeats well from test to test.
- Weaknesses
- A minority report readings that run a few tenths of a dKH below other kits or an ICP lab, or that drift as a reagent bottle ages. Cuvettes must be spotless.
- Who it's for
- Reefers with stony corals who test alkalinity several times a week and want repeatable numbers.
- Expert consensus
- Reef2Reef users comparing kits found the Hanna the most repeatable (roughly 0.1 dKH test-to-test vs 0.2–0.3 for titration kits) while noting precision is not the same as accuracy. Randy Holmes-Farley cautions that Hanna's "standards" only check the colorimeter, not the method, so occasionally confirm against a different test. Hanna's own spec is ±0.3 dKH ±5% of reading.
Sources
Where to buy:
Hanna HI774 Ultra Low Range Phosphate Checker
Digital colorimeter
- What reviews say: strengths
- Owners say it ends the guesswork of reading faint blue colors at low phosphate, and gives consistent results when the procedure is followed the same way each time.
- Weaknesses
- The reagent wait is several minutes, reagent packets add up, and a few owners report units failing just past the one-year warranty.
- Who it's for
- Tanks running low nutrients, where the difference between 0.02 and 0.10 ppm matters.
- Expert consensus
- Reef2Reef users in kit-comparison threads favor Hanna's ultra-low-range phosphate checker over color-card kits for low readings, and one experienced user said they'd pick the ULR over the LR version given the same cost.
Where to buy:
Salifert KH/Alkalinity Test Kit
Titration kit
- What reviews say: strengths
- A sharp color change, a quick test, and low cost per test. Several reviewers keep using it even after buying a digital checker, and one matched an ICP lab result within 0.2 dKH.
- Weaknesses
- Reading the syringe is the fiddliest part, and endpoint interpretation varies between people.
- Who it's for
- Budget-conscious reefers and anyone who wants a reliable backup to cross-check a digital checker.
- Expert consensus
- In Reef2Reef comparisons, long-time users report repeatable results within about 0.3 dKH, while others found more scatter. That's why experienced hobbyists suggest using it as a second opinion alongside another method.
Sources
Where to buy:
Red Sea Reef Foundation Pro Multi Test Kit (Ca, KH, Mg)
Titration kit
- What reviews say: strengths
- One box covers calcium, alkalinity and magnesium. Many owners find it easy to read and feel it's better quality than entry-level kits.
- Weaknesses
- Some reviewers report inconsistent back-to-back results, a magnesium test that read high, and syringe markings that wore off.
- Who it's for
- New reefers who want all of the Big 3 in one purchase.
- Expert consensus
- Reef2Reef users report that Red Sea's alkalinity test is in the same repeatability range as Salifert, at about 0.2 dKH test-to-test.
Where to buy:
Salifert Nitrate Test Kit
Color test kit
- What reviews say: strengths
- Quick (about a 3-minute wait), affordable, and good for spotting whether nitrate is near zero, moderate, or high.
- Weaknesses
- Several reviewers find the colors hard to tell apart and treat it as a ballpark test rather than a precise one.
- Who it's for
- Routine nitrate checks on a budget. Use a digital checker if you need precision.
- Expert consensus
- We found no specific expert testing of this kit. The broader advice from experienced reefers in kit-comparison threads is to rely on trends from one consistent test and confirm odd readings with a second method.
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.