How to Lower Nitrate in the Aquarium


An aquarium a beautiful home piece that effortlessly brings out joy and takes away stress. Fish, plants, and other invertebrates can inhabit your aquarium well without constant monitoring and hassle maintenance. Aside from having a low-key pet, it also adds elegance to homes, offices, and other spaces.

Maintenance of an aquarium can be tiresome, especially if you don’t know where to start. Wondering how to lower nitrate in the aquarium is a valid thought to keep your fish healthy. Knowing more about nitrates will help you become a more responsible aquarium owner. Aside from that, it also keeps the water clean and the entire environment a hearty place to live.

Where Does Nitrate Come From?

Nitrate is an odorless and colorless gas that builds up over time in aquariums. They naturally come from plants and animals as waste products. Other things that contribute to the buildup of nitrates include uneaten food, unclean and old filters, and overcrowding of fishes inside an aquarium.

The waste product of your fish and the plants inside is primarily ammonia. Once released it is then converted into nitrate through a common process known as nitrogen cycle. Nitrate is the last link in this chain.

Nitrates are highly toxic to the living things inside the aquarium if their amount exceed the safe levels. If left in high concentrations, it can contaminate the water and can cause harm to fishes and plants. Filters work efficiently in lowering this out, and regular aquarium cleaning can help alleviate the amount of nitrates.

How to Lower Nitrate in the Aquarium?

Being a responsible fish owner entails you to lower down the nitrate levels from time to time. This process isn’t as tedious as you think because a lot of kits are available for personal use. Lowering down the nitrate content can improve the mood of your fish and the ambiance of your aquarium.

Denitrification is a process that significantly lowers down the nitrate levels. This process involves using a specialized nitrate filter that will neutralize nitrates while absorbing other toxic agents and contaminants.

Another way of lowering down the nitrate content in your aquarium is by having a complete water change. This also give you the chance to scrub off the inner glass walls that may have ammonia. Cleaning out the contents of the tank is also incorporated in this regular process.

How Nitrate Levels Affect Aquarium Fish?

Knowing that nitrate levels cause harm to the health of your fish isn’t sufficient. Nitrate comes directly from ammonia. It is a reactive molecule and when high levels are in the system of your aquatic friends, can cause a lot of disturbances in their daily lives.

Because their system isn’t used to having this amount of reactive molecule, it results in various signs and symptoms of toxicity. This nitrate toxicity can impose as behavioural changes that is observed in 24-48 hours. These changes include:

  • Laying on the bottom of the tank
  • Loss of appetite or changes in the way they eat
  • High respiration and rapid gill movements
  • Acting dazed; being listless
  • Disorientation; loss of balance
  • Curling of the head to the tail (seen in advanced stages)

Nitrates aren’t seen and there is no distinct smell when its levels are high. As their levels slowly rise up, more and more of your fishes will begin to exhibit symptoms. If these levels aren’t reduced or no remedy is done, your fishes will eventually die of toxicity.

Frequently Asked Questions


How to test nitrate in an aquarium? 

It is vital to know the nitrate level in your aquarium to keep the potential of nitrate toxicity at bay. You will need a reliable nitrate test kit to check this. There are a lot of nitrate test kits that are easy to use and almost always available in pet stores and aquarium shops.

Instructions on how to use nitrate test kits vary. But most kits will require you to match the color of the water with the color chart that is usually included. These color charts are labelled with the approximate amount of nitrates in the tank.

If you are not confident with how you test the nitrate levels on your own, there are pet shops or specialized aquarium centers that offer free water testing. Some of these shops also charge you for a decent price to check for nitrate levels.

How often should aquariums be tested for nitrates?

It is apparent that testing your aquarium with nitrate levels is essential. And testing nitrate levels should be part of your regular aquarium maintenance. However, testing the amount of nitrates daily is also unnecessary.

Testing your aquarium for nitrate levels is reasonably done once a month. These monthly tests are vital, especially if you are breeding fish. While you’re out testing your aquarium water, you can also check for the temperature, pH level and other parameters.

What level of nitrate in aquarium is safe?

Once you know how high or low the nitrate levels are, it is important to keep in mind the safe and dangerous levels. Knowing this will help you assess when to change your water, and go to the nearest vet in cases of excessively high nitrate levels.

A nitrate level of 5 to 10 ppm is considered ideal in most aquariums. Some aquarium enthusiasts have a ceiling of up to 20 ppm. At this same level of 20 ppm is considered to be high and dangerous. Levels at around 20-50 ppm can potentially harm the fish and levels of 100 ppm can cause instantaneous death.


Maintaining a healthy environment for your fish can be a challenging chore. Knowing how to how to lower nitrate in the aquarium gives you an edge in keeping the water safe and clean for your fish to swim through. Keeping nitrate levels low will also ensure that your aquatic pets are living their best lives inside.

Although nitrates are less toxic than ammonia, these levels can accumulate over time and can be harmful. Changes in behavior that you aren’t familiar with is a signal that your fish isn’t as healthy as before. Regular nitrate level check-ups will prevent you from having unhappy and moody fishes inside your aquarium.

Leave a Comment