Aquarium Test Reagents & Refills

12 replacement reagents and refill kits for Hanna Checkers, Neptune Trident and automated reef testing

Running out of reagent mid-test is the reason most reef keepers stop testing consistently. This is the replacement stock: Hanna Checker reagents in 25-test packs for alkalinity, calcium, marine magnesium, marine ammonia, high-range nitrate, ultra-low-range phosphate and phosphorus, and copper — plus Neptune Trident and Trident NP reagent kits in two-month and six-month sizes, and ABC automated testing reagents. Check which Checker model you own before ordering — phosphate and phosphorus use different reagents. Order a spare set before you need it.

Hydros

CoralVue HYDROS controllers, probes, sensors, dosers, power centers and automation accessories for saltwater and reef aquariums

Heaters, Chillers, and Thermometers

Reliable heating, cooling, and temperature monitoring for stable aquariums

Dosing Pumps

precision dosing pumps and multi-channel dosers for automated calcium, alkalinity, magnesium and trace element supplementation

Probes & Controller Accessories

Aquarium controller probes, sensors, cables, modules, pumps, power equipment, and automation accessories

Top picks

Top Reagent Picks

Compare the strongest options in this collection at a glance.

Best overall

Phosphate Ultra-Low Range (PPM) - Reagent 25 Pack - Hanna Instruments

Phosphate Ultra-Low Range (PPM) Reagent - 25 Tests - Hanna Instruments

Starting at $14.81

View details

6-Month Trident Reagent Kit - Neptune Systems

Starting at $109.99

View details

ABC Automated Testing Reagents

Starting at $31.89

View details

Trident NP Reagent - Neptune Systems

Starting at $59.99

View details

Answers

Aquarium Reagents FAQs

How long do aquarium reagents last?

Most reagents are good for 1–2 years unopened, but once opened, they should typically be used within 6–12 months for best accuracy. Always check the expiration date and store them properly.

Why do my results suddenly seem off?

The most common reasons are expired reagents, dirty testing vials, or not following the timing steps exactly. If you're getting unusual results, double-check your technique and try a fresh test.

Can I use different brands of reagents with my tester?

No — reagents are specific to the test kit they were designed for. Mixing reagents or using them with the wrong test equipment can lead to inaccurate results.

How should I store my reagents?

Keep them in a cool, dry place away from light and moisture. Avoid areas near your sump or tank where humidity can shorten their shelf life.

Do I need to calibrate my kits or testers regularly?

Manual kits don’t need calibration, but digital testers often require periodic calibration solutions (especially for pH or salinity). Follow the manufacturer’s instructions to keep everything accurate.

Dive deeper

Dive Deeper: Aquarium Test Reagents

These are consumables for the meters and automated testers you already own. Match the reagent to your instrument, not just to the parameter.

Hanna Checker Reagents

Sold in 25-test packs for the Hanna marine Checker range: alkalinity (dKH), calcium, marine magnesium, marine ammonia, high-range nitrate, ultra-low-range phosphate (ppm), ultra-low-range phosphorus (ppb) and high-range copper.

Phosphate vs. phosphorus — get this right. The ULR phosphate Checker reads in ppm PO4; the ULR phosphorus Checker reads in ppb P. They are different instruments with different reagents, and the numbers are not interchangeable (multiply ppb P by roughly 3.07 to get ppb PO4). Buying the wrong reagent pack is the most common ordering mistake in this category.

Neptune Trident and Trident NP Reagents

Reagent kits for the Neptune Systems automated testers, in two-month and six-month capacities. Trident covers alkalinity, calcium and magnesium; Trident NP covers nitrate and phosphate. Automated testers only stay accurate on fresh reagent — check the expiry, and store spares somewhere cool and dark rather than in the cabinet under the tank.

ABC Automated Testing Reagents

Reagents for ABC automated alkalinity testing systems.

Storage and Handling

Watch the expiry date. Expired reagent does not fail loudly; it reads wrong, and you dose against a wrong number.
Store cool and out of light. The stand under a reef tank is warm and humid, which is the worst place in the house for reagent.
Do not squeeze air into the packet when dispensing — it accelerates degradation of what is left.
Run a known standard periodically if you are making dosing decisions on the readings. A drifting reagent and a drifting probe look identical from the outside.