Red Sea Calcium Pro Testing Kit 75 Tests

• Titration rather than colour comparison – the endpoint is a distinct colour change you titrate to, so the reading does not depend on the light you are standing in.
• 5 ppm resolution – fine enough to track daily consumption, and to stay inside the 20 ppm maximum daily change Red Sea specifies.
• Professional one-handed titrator – leaves your other hand free to swirl the vial, which is what keeps consecutive tests consistent.
• 75 tests per kit – roughly eighteen months of weekly testing.
• Effectively unlimited range – a titration reads to its endpoint instead of running off the top of a printed scale.
• Refillable – the reagents are replaced on their own, so the titrator and glassware are a one-time purchase.

• Reagent A, 25 mL
• Reagent B, 20 g powder
• Reagent C (titrant), 75 mL
• Professional titrator, one-handed operation
• 5 mL syringe
• Dosing spoon for the powdered reagent
• Analysis-grade glass vial
• Colour reference card
• Instruction manual
• Durable plastic storage case

Not included: any calcium supplement. The kit measures calcium; it does not correct it. If the reading comes back low you will need Red Sea Foundation A (Calcium+) or an equivalent, bought separately. Alkalinity and magnesium each need their own test kit as well – this kit reads calcium only.

The three foundation elements are consumed together and are usually tested together. Each Pro kit covers one parameter.

If you are buying your first foundation test and expect to test all three, the Reef Foundation Pro Multi kit puts them in one case. If you already own the others, buy Calcium Pro on its own.

Red Sea publishes calcium targets as a deliberate trade-off between growth rate and coloration rather than as one correct figure.

Holding a figure steadily beats hitting a better figure occasionally. Red Sea caps safe movement at 20 ppm in a single day.

Check salinity first and correct it if needed, then wait ten minutes before drawing your sample. Red Sea's own instruction is explicit about this, and it is the step most people skip.

Level the powdered Reagent B in the dosing spoon against the edge of the container. A heaped spoon shifts the endpoint and produces a high reading that will not reconcile with your other tests.

Test at the same point in your dosing cycle each week. A sample drawn an hour after dosing and a sample drawn the night before are measuring two different things.

Low: dose Foundation A (Calcium+) and re-test in three days to establish your tank's consumption rate, then move to weekly testing.

High: stop dosing and let the corals draw it down. High calcium alongside high alkalinity risks precipitation, which strips both at once and leaves white scale on heaters and impellers.

On target but corals are not growing: test alkalinity and magnesium. Low magnesium makes calcium and alkalinity almost impossible to hold together, and correcting it is usually what fixes a reef that tests fine and still sulks.

Rinse the glass vial and syringe in RO water after each test and let them dry. Salt residue left in the vial carries over into the next sample.

Store the reagents closed in the case between 15 and 25 °C, away from prolonged light, and away from acids, oxidising compounds and bare metal. Red Sea states they are stable to the date printed on the pack when stored that way. When they run out, the Calcium Pro Reagent Refill restocks all three without replacing the titrator.

Reagent A carries the signal word Danger. Red Sea's safety data sheet lists it as containing 10–25% sodium hydroxide: it causes severe skin burns and eye damage and may be corrosive to metals. Wear gloves and eye protection when handling it, and keep it in its original labelled bottle.

Reagent C contains EDTA at 1–5%, carries the signal word Warning, and is an eye irritant. Reagent B is not classified as hazardous. Keep the whole kit out of reach of children. For eye contact, rinse with water for at least 15 minutes and seek medical attention.

Suitable for: reef aquariums running stony corals or clams, anyone dosing a calcium supplement or running a calcium reactor, and anyone whose current calcium kit gives readings they do not trust.

Not suitable for: freshwater aquariums, or testing general hardness. It measures one parameter only – alkalinity and magnesium need their own kits. For a fish-only marine tank with no stony corals, calcium testing at this resolution is more precision than the system needs.

• Red Sea Calcium Pro Reagent Refill – restocks all three reagents when the kit runs dry.
• Red Sea Foundation A (Calcium+) – the supplement this kit exists to meter.
• Red Sea KH/Alkalinity Pro Test Kit – the parameter consumed alongside calcium.
• Red Sea Magnesium Pro Test Kit – test this before troubleshooting either of the other two.
• Red Sea Reef Foundation ABC 3 Pack – all three supplements together.
• Red Sea Coral Pro Salt 20 kg – mixes to elevated foundation levels, so water changes support your targets.

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.

Ships as a standard small parcel. Reagent volumes are well under the threshold for dangerous goods freight.

How accurate is the Red Sea Calcium Pro Test Kit?

Red Sea specifies a resolution of 5 ppm. Because the method is a titration rather than a colour comparison, the measuring range is effectively unlimited – you titrate to an endpoint instead of matching a sample against a fixed printed scale.

How many tests are in the kit, and can I refill it?

The kit contains 75 tests. When the reagents run out, Red Sea part R21406 restocks Reagents A, B and C for another 75 tests, and you keep the titrator, syringe, dosing spoon, glass vial and case.

What calcium level should I run in a mixed reef?

Red Sea publishes 450 ppm as the balance point for great growth and great coloration in a mixed reef, 465 ppm if you are prioritising growth, and 430 ppm if you are prioritising colour. Whichever you choose, hold it steadily and do not move calcium more than 20 ppm in a day.

Does this kit test alkalinity and magnesium as well?

No. The Calcium Pro kit measures calcium only. Alkalinity and magnesium have their own Pro kits, or the Reef Foundation Pro Multi kit covers all three in one case.

Why do my two calcium kits disagree?

Reagent age is the most common cause – an out-of-date kit drifts. After that, check that you levelled rather than heaped the powdered reagent, that salinity was correct before sampling, and that the glass vial was rinsed and dry. Fresh reagents in a correctly run titration are the figure to trust.

Can I use it on a freshwater aquarium?

It is designed and calibrated for marine and reef water. For freshwater hardness a general hardness test kit is the appropriate tool and costs considerably less.