The Salifert Copper Test Kit (sometimes called Salifert COPT or Salifert Copper Profi-Test) is a colorimetric kit intended to measure dissolved or weakly chelated copper in aquarium (or pond) water. Copper Test Kit (Cu) it's designed to be sensitive enough for aquarists to monitor copper at low concentrations—useful during medication treatments, checking for contamination from tap water, or ensuring levels aren’t harmful to aquatic life.

Salifert indicates it works best when water pH is in the range of about 7.5 to 9.0, for the proper chemical reaction conditions.

One caveat: strongly chelated copper (i.e. copper bound tightly to strong chelating agents) may not be fully detected by the kit.

Copper is frequently used as a treatment for fish infected with parasites. However, maintaining the correct concentration is crucial, as excessive levels can be toxic to marine fish and invertebrates. Tap water may also naturally contain significant amounts of copper, making regular testing advisable.

Copper in water can exist in various forms, including dissolved ionic copper and weakly chelated copper (e.g., bound with citric acid). The Salifert Copper Test Kit is designed to measure both dissolved and weakly chelated copper accurately.

Accurate measurement of copper levels is essential, especially when using copper-based treatments. Overdosing can harm aquatic life, while underdosing may render treatments ineffective. Additionally, since tap water can introduce copper into the aquarium, regular monitoring helps maintain a safe environment for all inhabitants.

Sensitivity and Range: Detects copper concentrations from 0.05 mg/L to 2 mg/L, covering both low and high levels

Applicability: Suitable for both marine and freshwater aquariums .

Test Count: Provides approximately 50 tests per kit, allowing for multiple assessments

Ease of Use: Simple procedure with results available in about 20 minutes

Detection Capability: Measures dissolved and weakly chelated copper, ensuring comprehensive monitoring

The Copper Test Kit assesses dissolved and weakly chelated copper in a water sample. “Dissolved” means copper ions or species that are in solution (not precipitated or bound in solid form). “Weakly chelated” means copper ions that are loosely complexed with ligands (organic molecules) such that they can still undergo the color-reaction chemistry. Very strongly chelated copper (bound tightly in complexes) may not react or be partially “invisible” to the test.

When you carry out the test, you will compare the color of your sample to a color chart, and the color (intensity / hue) corresponds to a copper concentration in ppm (mg/L).

If your result is, say, 0.05 ppm (a light blue tinge), that implies a very low copper level. Higher readings such as 0.5 ppm, 1.0 ppm, or beyond reflect progressively higher copper concentrations. Because copper is toxic to many invertebrates (and even fish at high levels), the reading helps you judge whether the copper in the water is in a safe or hazardous range for your livestock.

If a copper medication is being used (for parasites, etc.), accurate measurement is essential, because overdosing is dangerous. The test helps ensure the dosage is within therapeutic but non-toxic levels.

Because the kit offers a relatively fine resolution at low copper levels (e.g. distinguishing 0.05, 0.10, 0.20, 0.50, etc.), it is a good tool for careful monitoring.

Again, because of the possibility of partial detection (especially with strong chelators), one should interpret results with some caution: the actual “total copper” present might be higher, especially if chelating agents are in the system.

How to use it 

1. Take a clean test vial and add a measured volume of water sample (for example, around 2 ml).

2. Add a certain number of drops of the copper reagent (often 5 drops) to the vial.

3. Swirl gently (for about 5 seconds) to mix the reagent with the water.

4. Let the mixture stand undisturbed for about 10 minutes to allow the reaction to develop. If you suspect copper is tightly bound or chelated (e.g. from medications), some instructions suggest waiting 20 minutes and comparing readings at 10 vs 20 minutes, taking the higher result.

5. After the waiting period, hold the test vial and compare its color (often a shade of blue) against a white background and the test’s color chart. The shade that most closely matches the chart indicates your copper concentration in ppm.
6. If the sample color lies between two chart values, you can infer an intermediate concentration (e.g. half-way between).

Some kits also note that if the blue tint is even lighter than the lowest chart entry (e.g. lighter than 0.1 ppm), that corresponds to about 0.05 ppm.

Advantages:

• Fairly sensitive method, capable of detecting down to ~0.05 ppm copper.

• Good resolution across a useful range (0.05 to 2.0 ppm) for aquarists.

• Relatively easy to execute compared to more sophisticated instrumentation (like atomic absorption).

• Useful for checking copper contamination in tap water, for validating dosing of copper medication, or ensuring copper levels are safe for sensitive species.

• Because it yields multiple tests per kit (around 50), it is cost-effective over time.

Limitations:

• Strongly chelated copper (i.e. copper tightly bound to strong chelators) may not be fully measured, so the test may underreport total copper in certain conditions.

• Color interpretation is subjective (you must visually match the shade). Small differences in perception or ambient lighting can lead to variation in readings.

• The reaction and color development depend on pH and other water chemistry factors; deviations from the optimal conditions (e.g. outside pH 7.5–9) can affect accuracy.

• Because it is a chemical colorimetric method, interference from other substances in the water (competing ions, organic matter) may affect the outcome to some extent.

• In cases of high copper (above the kit’s upper limit), you’ll only know it exceeds the maximum detectable concentration (i.e. “>2.0 ppm”) rather than exact value.

Practical tips for Copper Test Kit (Cu)

• Use clean, uncontaminated vials; rinse thoroughly with deionized water or tank water before sampling.

• Perform the test under consistent lighting and against a white background to improve accuracy in color matching.

• Let reagents and sample reach similar temperature (room temperature) to reduce thermal effects.

• If the color is ambiguous or between chart values, note it as intermediate.

• If you are using copper-based medications (e.g. for parasites), perform frequent measurements (e.g. daily) to ensure that copper stays within the therapeutic but safe window.

• When using chelating medications or copper complexes, consider doing the 10-minute + 20-minute reading technique (comparing at both times) to catch partially chelated copper.

• If your tap or source water has copper, test it before using it in your tank so you know baseline.

• Use this kit in conjunction with other water parameter tests (e.g. general hardness, alkalinity, ammonia, etc.) to get a fuller picture of water chemistry.