The Milwaukee MW11 Digital Total Chlorine Tester is a compact photometer designed to measure total chlorine in water. It is a useful instrument for aquarium keepers who want to check tap water, prepared replacement water and other freshwater sources before introducing them into an aquarium.

Chlorine and chloramine are commonly used to disinfect municipal drinking water. However, these disinfectants can be harmful to fish, shrimp, corals and beneficial bacteria in aquarium filtration systems.

The MW11 provides a quick digital measurement of total chlorine, helping you check whether your water treatment process has reduced residual chlorine to an acceptable level before using the water for aquarium maintenance.

With a measuring range of 0.00 to 3.50 ppm, a resolution of 0.01 ppm and no visual colour matching required, the MW11 offers a convenient alternative to interpreting traditional colour-based test kits.

Key Features

• Total chlorine measurement – measures total chlorine, including free and combined chlorine.

• Ideal for aquarium water preparation – check tap water and prepared replacement water before use.

• 0.00–3.50 ppm range – suitable for routine testing of water sources and treated water.

• 0.01 ppm resolution – displays readings in small increments.

• High measurement accuracy – ±0.03 ppm ±3% of reading at 25°C.

• Digital photometer – measures the colour reaction electronically, avoiding subjective visual colour comparison.

• No calibration required – ready for use with the supplied reagents.

• Compact and portable – convenient for aquarium rooms, fish facilities and water-testing work.

• Simple reagent-based testing – uses Milwaukee DPD powder reagents for total chlorine measurement.

Why Test Total Chlorine in Aquarium Water?

Chlorine-based disinfectants are widely used to make municipal water safe for human consumption. However, water that is suitable for drinking is not necessarily suitable for aquarium use without treatment.

Residual chlorine can damage fish gill tissue and harm sensitive aquatic organisms. It can also affect the beneficial bacteria responsible for biological filtration.

Some water supplies use chloramine, a disinfectant formed by combining chlorine and ammonia. Unlike free chlorine, chloramine can be more persistent and may not be removed simply by allowing water to stand.

Testing total chlorine is therefore particularly useful when preparing aquarium water from a municipal supply.

The MW11 helps you:

• Check incoming tap water before aquarium use.

• Verify the effectiveness of a dechlorination process.

• Test replacement water before carrying out water changes.

• Monitor water after carbon filtration or other treatment.

• Check water used in freshwater and marine aquarium preparation.

Total Chlorine vs Free Chlorine

Understanding the difference between free chlorine and total chlorine is important when preparing aquarium water.

Free chlorine refers to chlorine disinfectant present in its free forms, such as hypochlorous acid and hypochlorite.

Combined chlorine refers to chlorine that has reacted with ammonia or other nitrogen-containing compounds. Chloramine is an important example.

Total chlorine includes both free chlorine and combined chlorine.

This distinction matters because a test that measures only free chlorine may not identify all chlorine-based disinfectant remaining in the water.

The MW11 is designed specifically to measure total chlorine, making it useful when checking water supplies that may contain chloramine.

Digital Photometer – No Guesswork with Colour Charts

The MW11 uses a DPD reagent reaction and an electronic optical measurement system.

When the reagent reacts with total chlorine in the water sample, it produces a pink colour. The photometer measures the intensity of this colour using an LED light source and silicon photocell, then displays the result digitally in ppm.

This avoids the need to visually compare a sample against a printed colour chart.

The instrument uses an adaptation of USEPA Method 330.5.

How to Test Aquarium Water with the MW11

The MW11 uses a simple sample-and-reagent procedure.

1. Fill a clean sample cuvette with 10 mL of the water being tested.

2. Place the cuvette into the tester and close the cover.

3. Follow the instrument's zeroing procedure.

4. Remove the cuvette and add one Milwaukee MI524 total chlorine powder reagent sachet.

5. Replace the cap and gently shake for approximately 20 seconds.

6. Return the cuvette to the tester.

7. Allow the reaction time specified in the instrument procedure.

8. Read the total chlorine result directly from the digital display.

Always follow the supplied Milwaukee instruction manual for the complete measurement sequence and timing.

What Should the Total Chlorine Reading Be for Aquarium Water?

For aquarium water preparation, the objective is to achieve no detectable residual chlorine before adding the water to the aquarium.

A reading of 0.00 ppm on the MW11 indicates that total chlorine is below the instrument's detectable reading at its displayed resolution. It does not prove the absolute absence of every chlorine compound.

If a reading is detected after water treatment, do not assume the water is ready for aquarium use. Review the water-conditioning process and test again before introducing the water.

For supplies treated with chloramine, use a conditioner specifically suitable for chloramine removal or treatment. Follow the manufacturer's instructions for the water conditioner and allow the recommended contact time before testing.

Suitable Aquarium Applications

The Milwaukee MW11 is particularly useful for:

Freshwater aquariums
Check tap water and replacement water before water changes to help prevent accidental introduction of residual disinfectants.

Marine and reef aquariums
Test source water and prepared replacement water as part of a wider water-quality management routine. The MW11 measures total chlorine; it does not measure salinity, alkalinity or other reef-water parameters.

Shrimp and sensitive fish systems
Use total chlorine testing as an additional precaution when preparing water for sensitive aquatic livestock.

Aquaculture and fish facilities
Check incoming water and treated water used in fish-holding, hatchery and production systems.

Water filtration systems
Monitor source and treated water to help assess chlorine removal performance.

Reagents and Maintenance

The MW11 requires Milwaukee MI524 total chlorine powder reagents for testing.

The meter is supplied with six reagent sachets. Additional reagent packs are available separately:

• MI524-25 – total chlorine powder reagents, 25 tests.

• MI524-100 – total chlorine powder reagents, 100 tests.

Keep the glass cuvettes clean and free from fingerprints, scratches and residue. Rinse them after use and wipe the outside with a suitable lint-free cloth before placing them in the instrument.

Use fresh reagents and follow the prescribed sample volume and reaction time to maintain reliable results.

Technical Specifications

Specification	Details
Model	Milwaukee MW11
Measurement	Total chlorine
Measuring range	0.00–3.50 ppm
Resolution	0.01 ppm
Accuracy	±0.03 ppm ±3% of reading at 25°C
Typical EMC deviation	±0.01 ppm
Measurement method	Adaptation of USEPA Method 330.5
Reagent method	DPD powder reagent
Light source	LED at 525 nm
Light detector	Silicon photocell
Calibration	No calibration required
Sample volume	10 mL
Operating environment	0–50°C, maximum 95% RH non-condensing
Power supply	1 × 1.5V AAA battery
Auto shut-off	After 2 minutes of non-use
Dimensions	87.5 × 63.7 × 35.2 mm
Weight	Approximately 65 g

Supplied With

• Milwaukee MW11 digital total chlorine photometer

• Two sample cuvettes with caps

• Six total chlorine powder reagent sachets

• 1 × 1.5V AAA battery

• Instruction manual

Important Information

The MW11 measures total chlorine in a water sample. It does not remove chlorine or chloramine, and it is not a general-purpose aquarium water tester.

For complete aquarium water-quality monitoring, use it alongside appropriate tests for pH, ammonia, nitrite, nitrate and other parameters relevant to your aquarium.

Protect your aquarium before every water change. The Milwaukee MW11 provides a convenient digital way to check total chlorine in tap water and prepared aquarium replacement water before it reaches your fish and biological filter.