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PO4 Test

Phosphate test for fresh and saltwater aquariums



Measuring range & accuracy

Measurement range for freshwater: 0.03 - 3.0 mg/l (ppm)

Measurement range for saltwater: 0.03 - 3.0 mg/l (ppm)

Accuracy: 0.05 mg/l (ppm)


About phosphate

Phosphates are important nutrients for all plants and are vital for the energy metabolism of every living cell. Phosphates are released into the aquarium water via food and the decomposition process of organic matter. However, an unregulated increase in the phosphate concentration creates problems, such as significant algae growth. In addition, phosphates in salt water aquariums can seriously inhibit the deposition of calcium carbonate in the skeleton formation process of hard corals and, in turn, for their growth. On the other hand, there can be a shortage of phosphate if there is a high stock of plants and / or corals and a low fish population. In this situation, phosphate will need to be added.

In freshwater applications, a phosphate concentration of up to 0.4 mg/l (ppm) is suitable, however 1 mg/l (ppm) should not be exceeded. Even a concentration of 0.02 mg/l (ppm) is adequate for supplying aquatic plants with nutrients. The phosphate concentration in natural saltwater is approximately 0.06 mg/l (ppm). We recommend that you prevent the concentration of phosphate from rising above 0.15 mg/l (ppm) in saltwater tanks and keep the concentration between 0.03 and 0.1 mg/l (ppm) in reef aquariums. To monitor this effectively, the phosphate concentration in the aquarium water should be tested regularly.

Package contents 

  • 18 ml / 0.60 fl.oz. of reagent A

  • 8 ml / 0.27 fl.oz. of reagent B

  • 2 glass cuvettes 10 ml

  • 1 dosing syringe 5 ml

  • 1 colour card

  • 1 comparator

  • 1 instructions for use



Instructions for use

  1. Shake the dropper bottles before use! Assemble and prepare the comparator.

  2. Rinse out both glass cuvettes with tap water and then several times with aquarium water.

  3. Fill each glass cuvette with exactly 5 ml of aquarium water using the dosing syringe. Put one of the two water samples aside as a reference.

  4. Add 10 drops (for saltwater) or 12 drops (for freshwater) of test reagent A to the test cuvette, close the glass cuvette using the stopper and briefly shake the sample.

  5. After that, add 4 drops of test reagent B, close the glass cuvette once again and briefly shake it.

  6. After 2 minutes of development time place the open test cuvette and the reference cuvette with the water sample into the comparator. Place the comparator on the colour card in such a way that the reference cuvette is sitting on a coloured field and the test cuvette on a white field.

  7. Now compare the opposing fields. To do this, look into the open cuvettes from above. Move the comparator on the colour card until both cuvettes match exactly.

  8. Read off the phosphate concentration under the relevant colour field. If the colours do not match exactly, an intermediate value can be estimated.

  9. Rinse out the glass cuvettes and the syringe thoroughly with tap water after the measurement process. 


Shelf life and storage:

6 months after opening. Store in a cool, dark place.


Measures in the event of unfavorable values

If the phosphate concentration in the water is too high, we recommend:


Frequently asked questions

Answers to frequently asked questions about this product can be found in our FAQ section.

Container sizes

PO4-Test                       Art. Nr. 28250                                                              Refill Pack                  Art. Nr. 28778


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