API Calcium Test Kit Liquid 1.25oz Saltwater
Water type
Saltwater
API Calcium Test Kit Liquid 1.25oz Saltwater
Know your calcium before your corals tell you the hard way. The API Calcium Test Kit measures calcium in saltwater and reef aquariums by liquid titration — the mineral stony corals, coralline algae, clams and other calcifying invertebrates draw down continuously to build skeleton and shell. A reading here tells you whether your dosing is keeping up with what the tank is actually consuming.
Key features
- Titration method — count reagent drops rather than read a colour gradient, which gives a more precise result than a dip strip.
- Reads as low as 20 mg/L — sensitive enough to catch calcium depletion well before it shows up as slowed coral growth.
- Saltwater and reef specific — calibrated for the 400–500 ppm range a reef tank actually runs in, not a freshwater range that doesn't apply.
- Simple kit, no equipment — test tube, two reagent bottles and a colour-matched instruction card.
Specifications
| Type | Liquid titration test kit |
|---|---|
| Measures | Calcium (Ca) |
| Water type | Saltwater / reef |
| Range | Readable to 20 mg/L |
| Target reef range | 400–500 ppm (mg/L) |
| What's included | 2 reagent bottles, 1 capped test tube, colour-matched instructions |
| Recommended testing frequency | Weekly |
How to use
Fill the test tube to the marked line with tank water, add the first reagent, then add the second reagent one drop at a time, swirling and counting until the colour changes. Each drop typically represents a fixed increment of calcium concentration — follow the conversion on the included card, since API does not publish a universal drops-to-ppm multiplier that applies across all its titration kits.
Suitable for, and not suitable for
Suitable for:
- Reef tanks with stony corals, soft corals, clams and coralline algae
- Fish-only saltwater systems where you also dose calcium for pH stability
Not suitable for:
- Freshwater aquariums — this kit is formulated and calibrated for saltwater
Goes well with
- API Copper Test Kit — copper is lethal to the same invertebrates that depend on stable calcium.
- API Deluxe pH Test Kit with Liquid Adjusters — calcium and pH interact; a full picture needs both.
Warranty and delivery
This is a consumable test kit, so no manufacturer warranty period applies. This does not affect your rights under the Australian Consumer Law: if the product is faulty, unsafe or not as described, you are entitled to a remedy. Ships as standard freight.
Common questions
What calcium level should a reef tank run at?
API's guidance for reef aquariums is a calcium concentration between 400 and 500 mg/L (ppm). Most stony coral and clam keepers dose to hold within that band and test weekly to catch drift before growth slows.
How often should I test calcium?
API recommends weekly testing for saltwater tanks. Calcium demand rises with coral growth and stocking, so a tank that is growing well can draw down faster over time and may need more frequent checks.
How many tests are in the kit?
API does not publish an exact test count for this kit on its own product information — unlike its colour-chart kits, a titration kit's test count depends on how many drops each individual test uses, which varies with the sample's calcium level. Expect several dozen tests from a full kit at typical reef calcium levels.
Does low calcium affect fish, or only corals and invertebrates?
Calcium demand in a reef tank is driven mainly by calcifying corals, clams and coralline algae rather than by fish. A fish-only saltwater tank is far more forgiving of calcium drift, though calcium still contributes to overall water hardness and pH stability.
