Calcium & Magnesium Test Kit

Benchmark Calcium & Magnesium Test Kit

Overview

The Benchmark Calcium & Magnesium Test Kit is a titration-based test kit for measuring two core reef chemistry parameters in saltwater aquariums: calcium and magnesium. Using separate reagent steps for calcium and total hardness, it gives reef hobbyists a practical way to track two major elements that support coral growth, skeletal development, and overall system stability.

This kit is designed for routine reef testing with clear step-by-step procedures, easy-to-read syringe measurements, and conversion methods that help turn titration results into usable ppm values.

What It Does

This kit measures calcium in ppm and calculates magnesium in ppm using calcium and total hardness titration results together. It is useful for monitoring element consumption, checking dosing adjustments, and maintaining consistency in reef aquariums.

The calcium test uses a 5.00 mL sample and is calculated as:

Calcium (ppm) = mL calcium titrant used x 600

The magnesium result is calculated from the total hardness and calcium titration volumes:

Magnesium (ppm) = (1701.35 x mL total hardness titrant) - (363.87 x mL calcium titrant)

For example, if calcium titrant usage is 0.70 mL, the calcium result is 420 ppm. If total hardness titrant usage is 0.91 mL and calcium titrant usage is 0.70 mL, the magnesium result is 1294 ppm.

Who It’s For

This kit is intended for saltwater aquarium hobbyists who want a dependable way to monitor calcium and magnesium as part of routine reef maintenance. It is well suited for mixed reefs, SPS systems, LPS systems, nano tanks, and larger marine aquariums where stable major-element levels matter.

How to Use

Calcium Test

1. Add 5.00 mL aquarium water to the test vial.
2. Add 1.00 mL of 4% sodium hydroxide.
3. Add one level scoop of calcium indicator powder.
4. Swirl until the sample becomes pink.
5. Slowly add calcium titrant while swirling.
6. Stop when the color changes to purple.
7. Calculate calcium using: mL x 600

Total Hardness / Magnesium Test

1. Add 5.00 mL aquarium water to a clean vial.
2. Add 0.50 mL pH 10 hardness buffer.
3. Add 2 drops of calmagite indicator.
4. Slowly add total hardness titrant while swirling.
5. Stop when the solution turns pure blue with no red or purple tint remaining.
6. Use the calcium and total hardness readings together to calculate magnesium.

For best repeatability, use clean vials and syringes and read the endpoint under bright, neutral lighting.

What’s Included

• 118 mL calcium titrant bottle
• 118 mL total hardness titrant bottle
• 118 mL 4% sodium hydroxide bottle
• 118 mL pH 10 hardness buffer bottle
• Calmagite indicator bottle
• Calcium indicator powder container
• 0.15 cc scoop
• 1 mL syringes
• Glass test vials
• Instruction card

Typical Reef Range

• Calcium: 380-460 ppm
• Magnesium: 1200-1400 ppm

Important Notes

• Designed for 5.00 mL sample volume testing
• For saltwater aquarium use
• Careful syringe reading and endpoint observation are important for reliable results
• Store reagents sealed at room temperature
• Protect indicator solutions from light and keep powder reagents dry
• Keep out of reach of children

Purchase Confidence

The Benchmark Calcium & Magnesium Test Kit gives reef hobbyists a practical way to monitor two essential major elements with one organized testing system. It is built for routine reef use, with dedicated reagents for calcium and magnesium testing, clear result formulas, and the tools needed to run the tests consistently.

It is a good fit for hobbyists who want a dependable calcium and magnesium testing option for ongoing reef maintenance and dosing verification.