API KH Hardness Mini Test Kit
Water type
Freshwater + Marine
API KH Hardness Mini Test Kit
Tracks carbonate hardness – the buffer that keeps pH from crashing. The API KH Test Kit is a liquid reagent test for carbonate hardness (KH), also called alkalinity, in fresh or saltwater. A low KH is one of the most common reasons a stable-looking tank suddenly swings on pH, and this kit is how you catch it before that happens.
Key features
- Drop-count titration – add the reagent drop by drop and count until the colour changes; no colour chart matching required.
- Fresh and saltwater – one kit, one reagent, for either water type.
- Each drop is a known increment – API's KH reagent chemistry is built so one drop equals 1° dKH, giving you a precise number rather than a colour band.
- Tests vary with your water – softer water changes colour in fewer drops, harder water takes more. API does not publish a fixed tests-per-kit count for this reason.
How to use it
- Fill the supplied test tube to the 5 mL line with a water sample.
- Add the KH reagent one drop at a time, swirling the tube after each drop.
- Count the drops until the sample's colour changes.
- The number of drops added is your reading in ° dKH.
Specifications
| Measures | Carbonate hardness (KH) / alkalinity |
|---|---|
| Method | Drop-count titration |
| Resolution | 1 drop = 1° dKH |
| Sample size | 5 mL |
| Tests per kit | Not fixed – varies with water hardness; not published by API |
| Water type | Freshwater and saltwater |
| Freight | Standard |
What's included / what you'll still need
Included:
- KH reagent bottle
- Capped glass test tube
- Instruction booklet
Not included:
- A GH (general hardness) reagent – this kit measures KH only. See API GH/KH Hardness Test Kit for both in one box.
- Any product for raising or lowering KH
Suitable for, and not suitable for
Suitable for:
- Freshwater and marine tanks where pH stability is a concern
- Reef tanks tracking alkalinity alongside calcium and magnesium
- Diagnosing unexplained pH drift between water changes
Not suitable for:
- Measuring general hardness (GH) – a separate reagent is needed for that
- Adjusting KH on its own – this kit reads the number, it does not change it
Safety and handling
- Keep out of reach of children.
- Avoid skin and eye contact with the reagent; rinse with water if contact occurs.
- Store the reagent bottle capped and out of direct sunlight.
Goes well with
- API GH/KH Hardness Test Kit – adds general hardness (GH) to this kit's KH reading.
- API Freshwater Master Multi Test Kit 5 in 1 – pairs KH with ammonia, nitrite, nitrate and pH.
Warranty and delivery
This is a consumable test kit, so no manufacturer warranty period applies. That 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 KH should my tank be?
API does not publish a single target on this kit's own page. As general aquarist reference points rather than an API specification: most community freshwater tanks are commonly kept in the 3–6° dKH range, and harder-water setups such as African cichlid tanks are often kept well above that. Check the requirements for your specific fish or coral rather than relying on a generic figure.
Why doesn't API state how many tests are in the kit?
Because the test count depends on your water. Every drop is part of one test's worth of reagent, and a harder-water sample needs more drops – and therefore uses more reagent – to reach the colour change than a soft-water sample does.
Does this kit test GH as well as KH?
No, this is a KH-only kit. API's GH/KH Hardness Test Kit tests both in the one box, with a separate reagent bottle for each.
Can I use this in a saltwater reef tank?
Yes, API rates this kit for both freshwater and saltwater, which includes reef tanks tracking alkalinity.
