Summary: When testing aquarium water at home, an aquarium water test pen is the easiest option: calibrate with purified water, take water from the middle layer of the tank, insert the probe at an angle to expel air bubbles, tap to test, and view the radar chart and AI suggestions. The Water Detective Aquarium Edition gives 9 results at once, with no reagents needed.
Keywords: how to test aquarium water quality, aquarium water quality testing methods, how to use an aquarium water test pen, using the Water Detective Aquarium Edition
One-sentence answer: For aquarium water, it is best to test once a week at a fixed time, and once before and once after each water change. With the Water Detective Aquarium Edition, follow the five steps of "calibrate—take water—insert—test—read the interpretation" to see 9 results such as organics and turbidity within one minute, and the AI in the mini program will tell you whether you need to change the water.
Step 1: Calibrate with purified water
Calibrate before first use. Use bottled purified water such as C'estbon or Wahaha, not mineral water. Long-press the M key for about 5 seconds to enter calibration, or tap calibration in the mini program.
Step 2: Take water from the tank
Use a clean cup to take water from the middle layer of the aquarium, avoiding the outlet and the bottom sand. You can also put the probe directly into the aquarium to test, but avoid airstones and areas with strong water flow.
Step 3: Insert the probe at an angle to expel air bubbles
Remove the white outer cover and rinse the probe with tank water first. Insert the probe into the water at an angle and shake it gently a few times to drive away air bubbles. Air bubbles will make the readings fluctuate.
Step 4: Tap to test and check the screen
Tap the M key to start testing. The color screen first displays a radar chart and an 100-point total score (Excellent/Good/Fair/Poor); whichever corner of the radar chart is pulled inward is the weak item. Turn to page 3 to see each item's value: blue excellent, green good, yellow attention, red over limit. After the pen is taken out of the water, the results will remain on the screen.
Step 5: Check the AI interpretation and history
Turn on Bluetooth and location on your phone, and the results will automatically sync to the WeChat mini program "Water Detective". By default, the AI analyzes according to freshwater ornamental fish tank standards and tells you whether organic matter is too high, whether you should change the water, and whether you are feeding too much. By looking at weekly results together, you can find the water-change rhythm that suits your own tank.
When to test
| Timing | Why |
|---|---|
| A fixed day every week | Establish the "normal values" for your own tank |
| Before and after a water change | See the effect of the water change and also test the new water along the way |
| When setting up a new tank or after adding new fish | The water body is unstable and changes quickly |
| Water turns white, yellow, or smells, or fish behave abnormally | Test first, then treat—don't blindly replace the water |
| After cleaning the filter media | Observe whether the water fluctuates |
Frequently Asked Questions
Q: Do I need to buy reagents? No. Water Detective uses optical + electrode detection; you only need 7 batteries (2 batteries are enough to power it on, 4 batteries are more durable).
Q: Do I need to clean it after testing? Rinse the probe with clean water and put the outer cover back on. Remove the batteries when not in use.