Fritz Alkalinity (KH) Test Kit

The Fritz Alkalinity (KH) Test Kit is a liquid titration test that measures carbonate hardness (KH) — your aquarium's pH buffering capacity — in both freshwater and saltwater systems. Stable alkalinity is the single biggest factor behind stable pH, healthy coral growth, and a thriving African cichlid or planted tank. Pair with the rest of our water testing kits and additives & supplements.

Why This Test Kit

• Drop-counting titration — accurate enough for reef tanks where 1 dKH matters and easy enough for first-time freshwater testers.
• Works in freshwater and saltwater — one kit covers reef, FOWLR, African cichlids, planted tanks, and standard tropical communities.
• Pin down pH problems at the source — pH swings almost always trace back to low alkalinity; testing KH is faster than chasing pH crashes.
• Reef-tank essential — alkalinity is one of the "Big 3" reef parameters (with calcium and magnesium); test 2–3 times per week when dosing.
• Made in the USA by Fritz Aquatics, the brand behind our full Fritz lineup of conditioners, salts, and additives.

How to Use

1. Rinse the included test tube with aquarium water, then fill to the marked line.
2. Add reagent drops one at a time, swirling after each drop, until the color changes per the kit's instructions.
3. Multiply the drop count by the conversion factor on the label to get your KH/alkalinity in dKH or meq/L.
4. Record the result in your tank log and adjust dosing or water-change schedule as needed.

Target Ranges

Specifications

Recommended Pairings

• Fritz RPM Liquid PT 1 Alkalinity — dose alkalinity directly after testing reveals low KH.
• Fritz RPM Liquid PT 2 Calcium — the calcium half of the reef "Big 3" you should test alongside KH.
• Fritz RPM Liquid PT 3 Magnesium — the third reef parameter; KH and Ca won't stay stable without magnesium in range.
• Fritz Rift Lake Cichlid Buffer — raises pH and KH for African cichlid systems.
• Fritz Master Test Kit — multi-parameter bundle if you want full coverage.

FAQ

What's the difference between KH and pH?
pH is the current acidity/alkalinity reading at one moment. KH is the water's resistance to pH change — it's the buffer. Low KH means pH swings happen fast and crash hard; healthy KH keeps pH locked in place.

How often should I test KH?
Reef tanks: 2–3 times per week, especially if you're dosing or running a calcium reactor. Freshwater: monthly is usually enough unless you're keeping species (discus, African cichlids) with strict requirements or you've seen pH swings.

Is dKH the same as alkalinity in ppm?
They measure the same thing in different units. 1 dKH ≈ 17.86 ppm CaCO₃ ≈ 0.357 meq/L. The instructions include a conversion chart.

Why does my KH drop in a reef tank?
Corals consume alkalinity as they build skeleton; CO₂ from gas exchange also lowers KH over time. Test, then dose alkalinity supplement to replace what's used.

Can I use tap water if my KH is low?
Tap water KH varies widely by area. If your tap is high-KH, water changes alone can keep alkalinity stable in freshwater. For reef or low-KH freshwater species, RO/DI plus targeted remineralization gives more control.