Fritz Calcium Test Kit

The Fritz Calcium Test Kit is a liquid reagent test that measures calcium in saltwater and freshwater aquariums. It is a drop-count test that reads from 20 to 520 mg/L, and each drop of the second reagent equals 20 mg/L. See all of our water testing supplies.

What's in the Box

• 2 reagent bottles, 1.25 fl oz (37 mL) each
• A test tube
• An instruction card with chart

Why Test Calcium

Fritz explains that calcium is especially important in reef aquariums, where corals and other invertebrates use it to build their skeletons. Calcium should stay in proper ionic balance with alkalinity (KH) and magnesium, and a level outside that balance can lead to poor coral skeleton growth and tissue necrosis. Because corals actively consume calcium, levels in reef tanks can drop quickly, so regular testing is needed for proper dosing.

Fritz also notes that freshwater aquariums benefit from calcium monitoring. Plants need calcium for proper leaf growth, and shrimp and snails need the right amount to maintain their shells and avoid molting problems.

How to Test

1. Fill the test tube to the 5 mL line with aquarium water.
2. Add 10 drops from Bottle #1, holding the bottle upside down and completely vertical. Cap the tube and shake gently to mix.
3. Shake Bottle #2 vigorously for at least 10 seconds.
4. Holding Bottle #2 vertically, add one drop at a time, shaking gently between drops and counting each one. Stop when the solution turns from pink to blue. It passes through purple first, and usually only 1 to 2 more drops are needed after purple appears.
5. Multiply the number of drops by 20 to get calcium in mg/L.

Keep test solutions out of the aquarium and follow the full instructions in the box.

Reading Your Results

Typical calcium levels from Fritz:

• 75+ mg/L: tropical community fish
• 120+ mg/L: African cichlids
• 300 to 400 mg/L: marine aquariums
• 400 to 450 mg/L: reef aquariums

When raising calcium, Fritz advises making sure alkalinity (KH) and magnesium are also within ideal ranges. To lower calcium, do partial water changes with lower-hardness water such as RO/DI.

Specifications

Related Fritz Tests

• Fritz Alkalinity (KH) Test Kit, since calcium and alkalinity need to stay in balance.
• Fritz Phosphate Test Kit, since high phosphate inhibits calcification.

FAQ

How do I read the result?
Count the drops of Bottle #2 it takes to turn the sample from pink to blue, then multiply by 20 to get calcium in mg/L.

Does it work in freshwater?
Yes. Fritz states it measures calcium in both saltwater and freshwater aquariums.