How to Water Test your Freshwater Aquarium

If you’re new to the world of fishkeeping, then you may not be too familiar with water testing your freshwater aquarium. You may even be wondering if water testing is necessary at all, but to sum it up, yes, it is! Water testing is critical in newly set up aquariums to avoid fish loss. This can occur due to rapid rises in nitrate and ammonia. But even in established aquariums, you still need to upkeep regular water testing to ensure healthy living conditions for your fish.

Water tests are so important that you should be factoring the regular cost of them in with your initial operating costs of maintaining your aquarium. If aquarium test kits are an expense that you feel you can not afford, then you can’t afford to keep an aquarium at all.

How to Test Your Aquarium Water

For an effective and efficient test, your best option is to choose a good, all-rounder aquarium tester kit, which will measure and pick up several irregularities. There are several key issues that you should particularly look out for, including pH, ammonia, nitrite and nitrate. High-quality mechanical, chemical and biological filters will be able to keep these compounds largely in check, but you must always be conscious that it is an issue of a delicate balance. This is why it is still important to regularly water test your aquarium.

To help you with testing your aquarium water, we have broken down the top components you should be monitoring. As well as detailed why they’re dangerous and what the acceptable levels are for your aquarium.


Ammonia is the number one fish killer that any fishkeeper needs to be aware of. It is especially elevated during the start-up stages of an aquarium, although it is still just as common and dangerous in established tanks.

Coming from uneaten food and fish waste, ammonia is the first stage of your tank’s nitrogen cycle. This also means it is a common presence in your aquarium and needs to be closely monitored to ensure any abundance of ammonia is treated and maintained properly. Levels of ammonia can spike due to improper filter maintenance, a lack of regular water changes or if your tank is overstocked or overfed.

In freshwater aquariums, you need to ensure that your ammonia levels sit at 0.0ppm or are otherwise undetectable. Anything higher than this will mean that your aquarium water is toxic for fish and needs to be treated with a quality ammonia removal solution. Another way to keep on top of your ammonia levels without relying on regular water tests is to install an ammonia sensor directly in your tank. This is a faster method of detecting ammonia issues so that you may deal with them sooner.


Nitrite testing in your aquarium should be a part of your monthly maintenance, as an elevation of nitrite in your tank is a huge red flag. Coming from the second part of the nitrogen cycle, nitrites are the result of natural bacterias in your tank breaking down ammonia. High nitrite levels can stress or kill fish and are also prone to elevation during the start-up of a tank, even after the aquarium water is initially cycled.

If you notice a fish is unwell or suspect one to die prematurely in your tank, then high nitrite levels may likely be the cause, and you should test your water at the first sign. Nitrite levels in your aquarium should be no higher than 0.0ppm. If you’re looking for a way to maintain nitrite levels, then choose a quality concentrated filter conditioner for use in freshwater tanks.


From the breakdown of nitrites come nitrates, which are not as toxic for fish as ammonia and nitrite, but still need to be closely monitored and maintained. High levels of nitrate can cause stress for fish and may also lead to algae problems in your aquarium. You can expect nitrate levels to rise over time, but you should be especially wary when having young fish in your aquarium as they are more sensitive to nitrate than adult fish.

Ensure that nitrate levels register below 40ppm in freshwater aquariums, and if you do notice an unacceptable elevation, then it can be eliminated with a water change. Alternatively, nitrate removal filter media/resins provide another option for keeping nitrate levels in check in your tank.


Finally, we recommend that you keep an eye on the pH levels in your aquarium, although this measure can vary depending on the types of fish that you keep. For freshwater community aquariums, we suggest keeping pH levels in the range of 6.5 to 7.5 as this is typically a safe level for freshwater fish. Investing in a pH sensor is a smart option and will alert you promptly when the pH level is up or down in your tank.

Our Tips for General Health

Now that you understand exactly what you should be testing for in your freshwater aquarium every month, don’t hesitate to explore our wide range of water tests and treatments available. Plus, we have also put together a few extra tips to help you ensure your aquarium is happy and healthy!

  • Keep an eye on water temperatures, and do your research to find the perfect temperature for your aquarium inhabitants.
  • To help remove nitrates, change at least 25% of your tank water every week.
  • Remove leftover food and fish waste with a gravel vacuum or other cleaning equipment.

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