• Home
  • /
  • Phosphate Test Kit for Freshwater and Saltwater - 75 Tests

Phosphate Test Kit for Freshwater and Saltwater - 75 Tests

1 Review


Test your aquarium water for inorganic phosphate which can sometimes be responsible for algae growth. This kit measures phosphates down to 0.1 mg per L. Easy to read results. For marine or fresh water.
75 tests.


Number of Tests75
Indicator MethodCOLOR CHANGE
Internal Id



1. Fill sample pipette to base of bulb and dispense to a test cavity of the test plate.
2. Add one drop of Phosphate Reagent 1. Add two drops of Phosphate Reagent 2. Stir briefly with stir rod.
3. After about 5 seconds to 30 seconds (or time frame that produces good matching with scale), compare color to chart to determine concentration.
4. Promptly dispose of completed test solutions by rinsing test cavity under running water. If the test plate becomes stained, soak or clean with a dilute bleach cleaner, then rinse well.

Reference test: The proper performance of this kit may be validated by running a test in the normal manner except that the reference sample is used in place of a aquarium sample. It is not necessary to run a reference test to use this kit. The only time you might choose to run a reference test is if you have cause to believe the test is giving incorrect results. If you run a test using the reference sample and obtain the correct result (based on the known reference value provided) then you know the test is giving correct results. To run a reference test, use the Phosphate Reference as the sample in a phosphate test. Reference value is 1.0 mg/L.

Hints: Sample volume is critical; you must use exactly one full stem of sample. Low phosphate levels generally develop faster (5-10 seconds) while higher levels take a bit longer (30 seconds). This kit is designed to measure low phosphate concentrations (< 0.05 to 3 mg/L). Very high concentrations will cause a precipitation of the reagent and consequently could be mistaken for a low reading. The appearance of tiny black or blue specks indicates beyond range concentrations. In such cases, prepare a known dilution of your sample with distilled water and test again.

Interpretation: This kit measures soluble inorganic phosphate, reported as phosphate, not phosphorus. To convert to phosphorus divide result by 3. Natural sea water ranges from less than 0.01 mg/L to 0.3 mg/L. For corals in reef aquaria, such phosphates should be 0.2 mg/L or less. Phosphates are non-toxic to ?sh and most invertebrates, but are ideally kept below 1 mg/L to minimize algae growth. In freshwater, phosphates are not critical and the allowable concentration is dependent on variables such as nitrate, manganese, iron, and vitamin concentrations, as well as the extent of use of live plants. Usually, freshwater phosphate concentrations will be beyond the range of this kit, and dilutions of the sample with distilled water will be required. If excessive algae growth is not a problem, then the phosphate concentration may be considered as acceptable.

Ratings & Reviews

1 review

  • 5 stars
  • 0 reviews
  • 3 stars
  • 0 reviews
  • 2 stars
  • 0 reviews
  • 1 star
  • 0 reviews

Good test kit, the instructions could have been organized better


This test kit comes with 2 testing reagents, a testing plate (that looks like a little square painter's palate with 6 divots), a pipette, a stirring rod, a gradient reference to compare for results,and a premixed phosphate solution for you to test the accuracy of the test. The gradient ruler is a nice idea, but it makes it a bit harder to decide what your reading is measuring out at, and while you are trying to decide the testing liquid stains the palate. The instructions inform you that it stains, but not until after the instructions about getting your reading, and it stains FAST. I would recommend using this test kit by a sink and making a decision about the reading as quickly as you can, and then rinsing it immediately to avoid staining. That said, it is easy to use and there are 6 divots, so you can get away with staining it 6 times before you have to buy a new palate.