Is Nitrate Good or Bad for Your Aquarium?

Photo of author


Is Nitrate Good or Bad for Your Aquarium?

If you search online for information about nitrate in fish tanks, many articles immediately pop up to warn you about the dangers of high nitrate and the best methods for lowering it. How much nitrate can be considered to be dangerous? And if nitrate is so toxic, why do many aquarium plant fertilizers increase nitrate levels when they are made to be safe for fish, shrimp, and snails? Let’s discuss nitrate, which is the most confusing aspect of aquarium hobby.


What is Nitrate?

The aquarium’s waste is a source of toxic nitrogen compounds, such as ammonia, which can be produced when fish and other animals eat or poop. Beneficial bacteria in the fish tank naturally grows and consumes the ammonia, purifying the water in the process and making it safe for fish to live in. One of the products that the beneficial bacteria produces is however


. Nitrate is significantly less toxic than ammonia, but in large amounts, it can also start to negatively impact animals. For more information, read The Easy Guide to the Nitrogen Cycle for Aquariums.

How to Measure Nitrate

Since nitrate can’t be seen with the naked eye, it is neither colorless nor odorless. Fishkeepers typically measure it using water test strips or chemically reacting kits. Aquarium Co-Op Multi-Test Strips measure nitrate quickly and five other parameters in under a minute. Just dip the test strip in the aquarium water until all test pads are covered. Then, gently swirl the strip underwater for 3 seconds. Then remove the test strip out of the fish tank without shaking off the excess water and keep it horizonal for 60 seconds. Compare the test results immediately with the color chart provided to see the amount of nitrate.

Use multi-test strips for measuring nitrate and other water parameters.

What are Safe Levels of Nitrate in Aquariums?

While some nitrogen waste compounds like ammonia and nitrite are toxic to animals at even trace amounts, nitrate is considerably less toxic. Unfortunately, not enough research has been done on how toxic nitrate can be to all the animals that we can keep in our aquariums. As a frame of reference, a research paper titled Nitrate toxicity to aquatic animals reports that nitrate concentrations were raised up to approximately 800 ppm before they became lethal to guppy fry. We recommend keeping fish tanks below 80-100 ppm of nitrate.

Many people see this upper limit for nitrate and assume that, for the health of their aquarium animals, it would be best to lower nitrate as much as possible. Although fish, shrimp, and snails are not affected by a lack of nitrate in their aquariums, they do need it for good growth. Plant leaves can become translucent or yellowish if the nitrate level drops below 0-20ppm. This is because the plant has to consume nutrients from the bottom to grow new leaves. Therefore, we aim to keep approximately 50 ppm nitrate in planted tanks.

Signs of nitrogen deficiency

How to Lower Nitrate In High Bioload Tanks

Fish tanks that are overstocked with fish or have few aquarium plants can lead to a naturally high level of nitrates. You can reduce nitrate levels quickly and easily by performing a partial waterchange. Take out 30-50% of the old, nitrate-laden water using an aquarium siphon and refill the tank with fresh, clean water. Generally speaking, we want to avoid shocking the fish by doing huge water changes, so if your nitrate level is far greater than 100 ppm, you may need to do multiple water changes over the course of several days to safely lower the nitrate. This flow chart will show you how to make water changes.

Since most people don’t enjoy doing frequent water changes, let’s look at some approaches for keeping nitrate levels lower in the first place. High nitrate is often seen in aquariums with high bioload – meaning that lots of fish poop, dead leaves, leftover food, and other rotting organics are in the water. The best ways to reduce nitrate over the long-term are to decrease the amount of fish and/or food that is put into the tank. If you are not interested in reducing the fish population, you can upgrade your aquarium or add large amounts of live plants. We love aquatic plants as they naturally consume nitrogen, which allows them grow more leaves and roots. Pogostemon.stellatus and water sprite, which are fast-growing, can eliminate nitrate faster than slow-growing plants like anubias.

Are Fish Poop and Aquarium Plants a Good Enough Fertilizer?

Besides light and water, plants require an exact mix of nutrients to give them the fundamental building blocks needed to survive and thrive.


are nutrients that plants consume in significant quantities (such as nitrogen, phosphorous, and potassium), whereas


There are trace amounts of nutrients that plants require, such as iron, manganese, and boron. It was believed that fish poop or uneaten fish foods were enough nutrients to support plant growth. However, in reality they don’t contain all the necessary nutrients in the correct amounts. Plants that are kept by beginners without fertilizer often suffer from serious nutritional deficiencies in a matter of months. To address this common problem, we developed Easy Green as an easy, all-in-one fertilizer to help keep plants healthy and well-fed.

As you can see in the list of nutrients above, the purpose of Easy Green is to raise nitrate (or nitrogen) and other nutrients so that plants have enough to consume. In fact, the percentages of nitrate, phosphate, and potassium are higher than the rest because they are macronutrients that your plants need in greater amounts. As a result, adding Easy Green will increase nitrate when measured by a water test strip or kit. In fact, the goal is to dose enough Easy Green until the nitrate level reaches 50 ppm.

How to keep the right amount of Nitrate in Aquatic Plants

How can we achieve the perfect concentration of nitrate in our aquariums without having too little or too much? Your planted aquarium should have a consistent amount of nitrate.

Too much nitrate

Easy Green may cause a rise in nitrate so you might be tempted not to use it anymore. Withholding fertilizer could result in plants being deficient in other nutrients, as well as nitrate. These are the steps to prevent this:

1. Perform a 50% water changing (or multiple 50% water changing every four days) until the nitrate level reaches 25ppm. 2. One pump of Easy Green for every 10 gallons water. Wait a few hours and test the water again. 3. The goal is to reach 50 ppm nitrate. If the nitrate level is still low, you can repeat Step 2. You will continue to apply fertilizer until it reaches 50 ppm. 4. Give the water a rest for 3-4 days, then test it again. If nitrate is already at 75-100 ppm, you will have to do another 50% water change. Consider removing some fish or adding more plants (especially fast-growing ones) to decrease the rate at which nitrate is accumulating.

Quick dosing using Easy Green all-in one fertilizer

On the other hand, if your planted tank always has too little nitrate, you should regularly dose fertilizer to avoid starving your plants. We recommend that you use 1 pump of Easy Green for every 10 gallons water.

For low light aquariums, you should do once per week. For medium-light aquariums, do twice per week.

If you find that your plant leaves are still developing holes and melting away, a customized dosing method may be needed, based on the nitrate level of the water.

Keep track of when you fertilized your tank and how much Easy Green you used. You will soon be able to calculate your custom dosing schedule. You can decrease the amount of light and/or CO2 injection if you’re having trouble dosing enough fertilizer to meet the nitrate goal. Keep in mind that aquariums can become larger or smaller as fish and plants are added to them. This will affect the amount of fertilizer that is required.

Don’t worry if you see nitrate levels higher than 0ppm. Nitrate is good for plants and even essential. Easy Green was created to be a beginner-friendly fertilizer. Simply add 1 pump for every 10 gallons to your plants and watch them grow.