API Reef Master Test Kit

The API Reef Master Test Kit covers the four parameters a reef tank lives or dies on, the ones a basic saltwater kit leaves out. If you keep stony corals or clams, calcium and alkalinity are not optional readings. Browse all of our water testing.

What It Tests

• Calcium, the building block corals pull out of the water to grow
• Carbonate hardness (KH), your alkalinity buffer and the first number to move when something is off
• Phosphate, the nutrient behind nuisance algae and stalled coral growth
• Nitrate, which you want low but not zero in a modern reef

What's in the Box

• Seven bottles of liquid test reagent
• Two computer-calibrated laminated color cards
• Four glass test tubes with snap-tight caps
• Holding tray and a step-by-step instruction booklet

How to Use It

• Follow the booklet per test; the calcium and KH tests are titrations, so you count drops until the color turns rather than matching a card.
• Add titrant one drop at a time and swirl between drops, or you will overshoot and read high.
• Test calcium and alkalinity together. One moving without the other usually means a dosing problem.
• Weekly is enough on a stable reef, more often if you are dosing or chasing a problem.

Specifications

Pairs Well With

• API Saltwater Master Test Kit for pH, ammonia and nitrite, which this kit does not cover.
• Hanna HI774 Phosphate Checker when you need to read phosphate far lower than a color card can resolve.
• Browse all of our test kits.

Frequently Asked Questions

Is this enough on its own for a reef?
Not quite. It skips pH, ammonia and nitrite, so most reefkeepers run it alongside the Saltwater Master Test Kit.

My calcium reading seems high.
Titrations overshoot easily. Add the titrant one drop at a time, swirling between drops, and stop at the first full color change.

Is a color card accurate enough for phosphate?
For spotting a problem, yes. For dialing in a low-nutrient system, a digital checker resolves far below what the eye can read off a card.

Do the reagents expire?
Yes. Check the date codes, and replace an old kit rather than trusting readings that do not add up.