The testing pads from the API 5 in 1 Test Strips product should change colors shortly after you dip and remove it from the aquarium. If the pads remain the same when it comes to colors, then there may be an issue.
To see how you can potentially fix this problem, you can take a look at this troubleshooting article from Aquarium Blueprints.
1. To start off, make sure that the strips haven’t expired; otherwise, the product may longer be effective. You should be able find the expiration date printed on the package or container.
2. Next, you should also make sure that you haven’t contaminated the strip before you dip it into your fish tank. If you exposed the pads to another liquid beforehand, then we recommend that you use a brand-new strip in order to re-test your tank water.
3. Furthermore, you should also make sure that you are dipping the strip correctly into your tank water.
The strip should stay below the water when you swirl it around two times. When taking the strip out, you need to do it with the pads facing upwards. Furthermore, you should avoid shaking off any excess water.
4. It is also important to note that the nitrate, nitrite and pH testing pads will take up to 30 seconds to change color once you remove the strip from the tank water. So, if you didn’t previously wait for that amount of time, then you can try re-testing with a new strip and then follow the proper procedures.
For the GH and KH testing pads, the colors should be changed right away.
5. There is a possibility that the testing pads are working correctly as the colors may end up appearing the same before and after you dipped the strip into the fish tank.
We suggest that you look at the pads of the strip and the color chart as closely as possible under well-lit conditions to see if you are able to spot the difference. You can also try comparing the tested strip to a brand-new strip to see if the colors have changed at all.