Red Sea Marine Care pH/Alk Test 100/55 Tests
Pack size
100 pH tests / 55 alkalinity tests
Water type
Marine
Part no.
R21455
Red Sea Marine Care pH/Alk Test 100/55 Tests
Test the pair that actually explains your marine water chemistry. The Red Sea Marine Care pH/Alkalinity Test Kit measures pH (100 tests) and alkalinity/KH (55 tests) in marine and reef aquariums — two parameters that move together, since a weak alkalinity buffer is the most common cause of a swinging pH.
Key features
- Two linked parameters in one kit — pH and alkalinity share the same causes and the same fixes, so testing them together tells you more than either alone.
- 100 pH tests, 55 alkalinity tests — enough for months of weekly testing on a single system.
- Colorimetric pH, titration-based alkalinity — pH develops colour in around 10 seconds and stays stable to read for 5 minutes; alkalinity is read by counting reagent drops to a colour-change endpoint.
- Comparison cards included — no separate colour chart to lose.
- Entry point into Red Sea's Reef Care Program — results line up with the dosing guidance for Red Sea's Reef Foundation supplements.
Specifications
| Parameter | Tests per kit | Range | Resolution / accuracy | Method |
|---|---|---|---|---|
| pH | 100 | 7.6 – 8.6 | ±0.2 | Colorimetric (liquid indicator + comparison card) |
| Alkalinity (KH) | 55 | 0 dKH and up | 1 °dKH / 0.36 meq/L (0.5 °dKH resolution using the 10 mL sample volume) | Drop-count titration to colour-change endpoint |
Which Red Sea test kit do I need?
This is the everyday tier of Red Sea's pH/alkalinity testing. If you're chasing tighter reef-tank precision — dosing a calcium reactor or a two-part system where a swing of a few hundredths matters — Red Sea's KH/Alkalinity Pro Test Kit uses a finer titration for higher resolution. For routine weekly monitoring on a fish-only or mixed reef system, this kit is the right level of precision.
Suitable for, and not suitable for
- Suitable for: marine and reef aquariums, fish-only and mixed reef systems.
- Not suitable for: freshwater aquariums — Red Sea markets this kit specifically for marine use.
What to do with the result
If alkalinity comes back low, Red Sea's own guidance ties this kit's results to its Foundation supplement range — Reef Foundation B for mixed reef systems, or KH-Coralline Gro in fish-only marine systems — dosed against the reading you get here. Stable alkalinity is what holds pH steady, so it's worth correcting alkalinity before adjusting pH directly.
Care and storage
Reagents are stable up to the date printed on the pack when stored closed between 15°C and 25°C. Keep the kit out of direct sun and away from the tank splash zone — reagent bottles that pick up tank water give false readings.
Warranty and delivery
Covered by the manufacturer's standard warranty against defects, in addition to your rights under Australian Consumer Law. Standard shipping across Australia.
Common questions
How often should I test pH and alkalinity?
Weekly on an established reef tank, and more often — every day or two — after a water change, a new coral addition, or any dosing change.
Does this kit include calibration or reference solutions?
No. The kit contains the pH indicator, alkalinity reagent, a sample vial, a syringe and two comparison cards — no separate calibration standard is included.
Why does my alkalinity reading keep drifting even though I dose consistently?
Coral growth and calcification consume alkalinity continuously, so a stable dose doesn't always mean a stable reading — increasing bioload usually means increasing demand. Retest after any change in stocking or growth rate.
Can I use this kit on a freshwater tank?
Red Sea markets this kit for marine and reef use. It is not intended for freshwater testing.
What's the difference between this kit and the Pro version?
Both measure the same parameters. The Pro kit uses a finer titration step for higher resolution, aimed at reef keepers chasing tighter precision — this standard kit is accurate enough for regular monitoring on most systems.
