How to Lower Nitrates in a Fish Tank

  • By:

    Alina A.
    Alina A.

    Author: Alina A.

    Alina Andreeva is a professional writer, editor, and pet-lover. She has published over 30 articles on how to care for pets properly. Alina has been writing articles for 3 years, so she has considerable experience in this niche. Her natural curiosity helps her to expand her knowledge and learn new pet care life hacks, which will make your life much easier.

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  • Updated on: 07/23/2020

Most fish keepers know all about the dangers of ammonia and nitrite within their tanks. However, the impact of nitrate is often less understood. Nitrate is not as lethal as either ammonia or nitrite, but it can still harm your fish. Therefore, it is essential to know how to regulate the levels within your aquarium. You need it for the good of your pets and the overall environment of the tank.

@David Clode

What causes Nitrate in a Fish Tank?

Nitrate can build up within a fish tank in some different ways. As a by-product of nitrite oxidation, some levels of nitrate can be found within the vast majority of tanks, no matter how careful you are. Decaying plant material can result in increased nitrate levels, as can detritus, and dirty filters. Besides this, overfeeding your fish can also raise the nitrate levels within the tank. Also, overstocking your aquarium with too many plants and fish for the space in question. Many people choose to fill their fish tanks with tap water when it comes to cleaning time. However, this can also add to the nitrate levels already within the aquarium. Some drinking tap water can contain 40 parts per million of nitrate. You should be aiming for a water source with around 10 parts per million or below. Nitrate-free water sources are ideal when it comes to filling your tank.

What is the Nitrate level safe for Fish?

In the wild, water nitrate levels within fish habitats are often deficient, around the five parts per million mark. Therefore, if you want to replicate the right natural conditions, you should be looking to reduce your nitrate levels as much as possible. If you are keeping a freshwater aquarium, the nitrate levels should never go above 50 parts per million, or else you risk causing significant damage to the fish within. Preferably, your nitrate levels should always be below the 25 parts per million mark, but the lower, the better. If you are looking to breed fish or reduce the number of algae growing within your tank, aim for a nitrate level of below 10 parts per million.

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What effect does Nitrate have on Fish?

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Fish will often begin to feel the effects of high nitrate levels once they reach between 50 and 100 parts per million. If left in conditions of this nature for a sustained time, the fish will start to develop health problems. Their immune systems will be weakened, making them more susceptible to disease and illness. Not only this, but their ability to reproduce will be inhibited by the high levels of nitrate. When it comes to young and fry fish, high nitrate levels can also affect their ability to grow. It is also important to know that many of the conditions that cause nitrate also cause a decreased level of oxygen within the water, heaping more stress upon your pets.

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What effect does Nitrate have on Algae?

The short story is, the higher your nitrate levels, the higher your chances of algae growth. The growth of undesirable algae is promoted at nitrate levels as low as 10 parts per million. As you rise above these levels, the growth of algae only increases further. Not only this but if your nitrate levels are rising faster than your healthy plants can use them, they will likely be overtaken by algae, before eventually dying.

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How do you lower Nitrates in an Aquarium?

Now that you know the dangers of high nitrate levels within your tank, it is time to learn precisely how to lower them and keep them low. It is essential to know that well-oxygenated filters will not allow nitrate-removing bacteria to thrive, as these bacteria avoid high oxygen environments.

  • Clean your tank regularly. The first and simplest step to reduce nitrate levels is to keep your tank clean. Waste produces nitrate. Therefore, a fresh tank is your best friend.
  • Feeding. As mentioned before, overfeeding can actually cause a rise in nitrate levels and other waste. Again, this is a simple fix. Only feed your fish the designated amount. Look at the back of the food packet/container for more information. If you notice that food is regularly being left by the fish, then reduce by a little each day until you reach the perfect amount.
  • Plants. Keeping live and healthy plants within your tank can reduce nitrate levels, as these plants use nitrate to survive. Just be careful that your nitrate levels stay at a reasonable level. Otherwise, these plants can be overgrown by algae.
  • Water changes. Changing the water within your tank should be a regular part of your schedule anyway. However, it is also essential to ensure that the water you are using is either low in nitrate or nitrate-free. If you have tested your tap water and found that it is high in nitrate, opt for deionized water or reverse osmosis water instead. However, mineral substitutes may be needed with these water types.
  • Equipment. If you have the money to invest in a filter that removes nitrate, then do so. If not, you can purchase nitrate-lowering media to help your existing screen achieve the same goal.

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