• Titration, not colour matching — you read a number off a syringe scale instead of holding a vial against a printed card under kitchen lighting.
• 0.05 meq/L (0.14 dKH) resolution — fine enough to separate a real trend from test-to-test noise, which a 1 dKH colour kit cannot do.
• 75 tests per kit — about nine months of twice-weekly testing on a single reef.
• Single-hand titrator — one hand works the plunger while the other swirls the vial, which is the difference between a repeatable endpoint and a rushed one.
• 100 mL Foundation B sample included — the buffer this kit exists to meter, enough to make your first correction before you commit to a full bottle.
• Reagent refills available — the titrator, syringe, vial and case are designed to outlast many bottles of titrant.

• Single-hand high-precision titrator
• Titrant, 68 mL — enough for 75 tests
• 10 mL syringe
• Analytical-grade glass vial
• Colour reference card
• Instruction manual
• 100 mL sample of Red Sea Foundation B (KH/Alkalinity)
• Chemical-resistant plastic storage case

• A full-size bottle of buffer. The 100 mL Foundation B sample is a starter, not a supply — Red Sea Foundation B is sold separately.
• Calcium and magnesium tests. Those are the Calcium Pro and Magnesium Pro kits, or all three together in the Reef Foundation Pro Multi Test Kit.
• A refractometer or salinity meter. Salinity has to be correct before an alkalinity result means anything.

There is no single correct figure. Red Sea publishes foundation targets by system type in its Foundation Supplements manual, and alkalinity only makes sense read alongside the calcium and magnesium it is balanced against.

Red Sea's wider Reef Care guidance spans roughly 7 to 12 dKH, trading growth rate against coloration. Pick a target, hold it, and move it slowly if you change your mind. Stability beats the number.

Below your target

Dose Red Sea Foundation B, the buffer this kit meters. Red Sea states a maximum safe increase of 1.4 dKH (0.5 meq/L) in a single day — going faster stresses corals rather than helping them.

Above your target

Stop dosing and let consumption bring it down, or dilute it with a water change. Do not chase alkalinity downwards with acid.

Drifting when nothing has changed

Calcium, alkalinity and magnesium move as a set. A stubborn alkalinity reading is usually low magnesium, so test all three before adjusting any of them.

Correct salinity before you test. An alkalinity reading taken at the wrong specific gravity is measuring the wrong water.

Rinse the glass vial in RO water between tests. Leftover titrant is one of the two things that quietly bias a result; the other is reagent age.

Store the titrant closed, in its original container, in the kit's case, cool and dry and out of direct sun. If a fresh bottle of titrant reads noticeably differently from the one you were finishing, trust the fresh one.

Red Sea's safety data sheet for this kit and its refill carries the signal word Warning. The titrant is listed as monoethylene glycol (an antifreeze-type solvent) at 50–75%, harmful if swallowed, and hydrochloric acid at under 1%, which can cause severe skin and eye burns and may irritate the airways.

Keep it out of reach of children and away from acids, alkalis, oxidisers and metals. In the eyes, rinse with plenty of water for at least 15 minutes and get medical attention. If swallowed, do not induce vomiting — rinse the mouth thoroughly and get medical attention.

Suitable for: reef aquariums of any size where corals are consuming alkalinity, anyone dosing a two- or three-part supplement and needing to meter it, and anyone whose colour-card kit reads the same before and after a dose.

Not suitable for: freshwater KH testing, where a low-cost colour kit is entirely adequate and this resolution is wasted. It also will not tell you calcium or magnesium, and it is not a replacement for a salinity check.

• Red Sea Alkalinity Pro Reagent Refill — part R21411, restores all 75 tests without rebuying the titrator.
• Red Sea Foundation B (KH/Alkalinity) — the full-size buffer you dose against the reading.
• Red Sea Magnesium Pro Test Kit — the parameter that explains most stubborn alkalinity readings.
• Red Sea Calcium Pro Test Kit — the third of the foundation trio.
• Red Sea Reef Foundation ABC 3 Pack — all three supplements together.
• Red Sea range — salts, supplements and the rest of the Reef Care program.

Reagents are consumables and carry no service warranty. Any manufacturer warranty Red Sea offers applies in addition to your rights under the Australian Consumer Law, which are not limited or excluded by it. A kit arriving with leaking, damaged or out-of-date reagents is replaced.

Ships as a standard parcel. The reagent volumes are well under the threshold for dangerous goods handling, so no special freight applies.

How accurate is the Red Sea KH/Alkalinity Pro Test Kit?

Red Sea specifies a resolution of 0.05 meq/L, which is 0.14 dKH. Because it is a titration rather than a colour comparison, the measurement is not bounded by a printed scale — you titrate to an endpoint and read the volume used.

How many tests are in the kit, and what does a refill cost me?

The kit contains 68 mL of titrant, enough for 75 tests. The reagent refill is Red Sea part R21411 and restores the full 75-test count, so you only ever buy the titrator, syringe, vial and case once.

Does the kit include the alkalinity supplement?

It includes a 100 mL sample of Red Sea Foundation B, which is enough to make an initial correction but is not an ongoing supply. A full-size bottle of Foundation B is bought separately.

Can I use this kit on a freshwater aquarium?

The chemistry will measure carbonate hardness in fresh water, but the kit is built around the resolution a reef needs. For a freshwater or planted tank a standard colour-comparison KH kit is cheaper and perfectly adequate.

My alkalinity keeps falling no matter how much buffer I dose. What is wrong?

Test magnesium. Magnesium holds calcium and alkalinity in solution, and when it runs low both of the others become impossible to hold no matter how much you dose. Correct magnesium first, then re-test alkalinity.

How often should I test alkalinity?

Red Sea's Reef Care approach is built on regular testing rather than a fixed interval, and most reefers with a stocked coral load test two or three times a week. On a new or heavily stocked system, test more often until the daily consumption rate is known.