Aquarium, Blog, Maintenance

Why Does My Fish Tank Have High Nitrates?

High nitrates, art of nitrate bottle

As you may or may not know, high nitrates in your fish tank can be a cause for concern. It can impact the health of your fish, shrimp, and snails and overall water quality. Understanding why nitrates can accumulate and how to manage it is essential for maintaining a healthy aquarium. This article will explore the most common causes of high nitrates, their effects on fish and plants, and provide practical solutions to keep nitrate levels in a good place.

Table of Contents

What Are Nitrates?

Nitrates are natural chemicals that result from the breakdown of ammonia and nitrite in the nitrogen cycle. Unlike ammonia and nitrite, which are highly toxic, nitrates are less dangerous, but can still cause problems when they accumulate in high amounts. High nitrate levels are often an indication of some kind of imbalance in the tank’s biological filtration and maintenance routine.

How Do Nitrates Form?

Nitrates are the final stage of the nitrogen cycle. They are form as a result of the natural process that breaks down organic waste (poop, food, and plants) in the aquarium. Here’s how nitrates form:

Ammonia to Nitrite

The nitrogen cycle starts with the conversion of ammonia (NH3) into nitrite (NO2-) by beneficial bacteria known in your tank. This bacteria lives in the substrate, surfaces, and most importantly, in your filter. Ammonia is produced from fish waste, uneaten food, and decaying organic matter.

Nitrite to Nitrate

Nitrite is then converted into nitrate by a second group of beneficial bacteria, which live in the same places as the other bacteria. This step is essential for reducing nitrite levels, as nitrates are less toxic and can be better tolerated.

Accumulation of Nitrates

The only unfortunate part is, Nitrates are not removed from the tank as easily as ammonia and nitrite, leading to it’s accumulation over time. Without taking some mitigating steps, Nitrates can continue to build up in your tank until there is algae, poor water quality, and even death. So, if you’re seeing some of those problems, read on, and we’ll talk about why and how to fix it.

Causes of High Nitrate Levels

There are several factors that can contribute to high levels of nitrate in your fish tank:

Overfeeding

This is the culprit for a lot of people, overfeeding. I get it, we LOVE our fish. They’re fun to feed and interact with, and let’s face it, they ALWAYS seem hungry. But, excess food decomposes in the tank, increasing ammonia production and subsequent nitrate levels. Feed only what your fish can consume within a few minutes to prevent excess food going bad in the tank. It’s difficult to have the self-control, but it will be worth it. If not for you, for the fish.

Overstocking

Overstocking is when you have too many fish for the size of the tank (number of gallons) or too poor of filtration for the amount of fish in the tank, or worse, both. Having too many fish in a tank can lead to rapidly elevated nitrate levels, as more poop is produced than the tank can handle. It’s important to research your fish, and only get 1-inch of fully grown fish per gallon in the tank. So a ten gallon tank can hold ten inches of fish (preferably smaller fish, because a 10-inch fish by itself should be in a much bigger tank than a 10-gallon).

Inadequate Filtration

Poor or insufficient filtration can also slow the breakdown of waste and lead to nitrate building up. Make sure your filter is equipped to handle the biological load of your aquarium and the fish in it. If not, consider upgrading. If you want to know more about your options for filters, take a look at our recent article on the topic.

Insufficient Water Changes

A water change is when you siphon water out of the tank, and add new, conditioned water, back into the tank. You should be doing this regularly. Most of my tanks, I do this weekly; however, I also have an elderly goldfish that I do water changes for every 4-5 days. He’s a little sensitive in his old age. Skipping regular water changes causes nitrates to accumulate. Water changes are vital for removing and diluting nitrates in order to maintain optimal water quality.

Decaying Plant Matter

If you’re struggling with plants, and there are dead ones in the tank, this may be a culprit as well. Dead or decaying plant material can contribute to nitrate levels as they breakdown. Regularly prune and remove dying plant parts to minimize nitrate production from decomposing organic matter.

Effects of High Nitrates

High nitrate levels can most definitely negatively effect your fish, shrimp, and plants:

Effects on Fish

Elevated nitrates can cause your fish to feel higher stress, leading to reduced immunity, sluggishness, and stunted growth. Prolonged exposure can also cause respiratory issues, increasing their susceptibility to diseases.

Effects on Shrimp

Shrimp are particularly sensitive to water quality changes, and high nitrates can lead to stress, failed molting, and also reduced reproduction rates. It’s crucial to maintain nitrate levels of 20 ppm or below for optimal shrimp health.

Effects on Plants

While nitrates serve as a nutrient for plants (nitrates are the primary compound in plant fertilizer), excessive levels can lead to algae blooms. And algae will compete with plants for light and nutrients. This imbalance can stunt plant growth and create an unstable ecosystem.

Solutions for Reducing Nitrates

Managing nitrate levels effectively requires a combination of a good setup and good maintenance. Here are some solutions:

Regular Water Changes

Perform weekly water changes. I do water changes of about 30%, but usually 20% is sufficient. If you find that a week after doing a 20% change your nitrates are still below 20ppm, congratulations! You can now try out 20% every two weeks. The main this is, consistent water changes are the most effective way to keep nitrate levels in check, and only you know your tank.

Maintain a Balanced Bioload

Do some math, and make sure your tank is not overstocked. Check that the fish population is appropriate for the tank size and filtration capacity is where it needs to be. Consider reducing the number of fish if necessary to maintain a balanced bioload. Sounds like an excuse to buy another tank 😉

Enhance Filtration

Upgrade your tanks filter if it’s needed to handle the biological load of your aquarium. Use high-quality biological filter media to promote the growth of beneficial bacteria that convert nitrates. Like a canister filter, they can handle almost anything if sized for the right tank (or bigger!).

Add Live Plants

Incorporating live plants into your aquarium can help reduce nitrates naturally and effectively. Plants absorb and eat nitrate as a nutrient, aiding in maintaining balanced water quality. Consider fast-growing species like hornwort or water wisteria, or even floating plants like Water Lettuce or Frogbit.

Use Nitrate-Reducing Products

If you’re really in a bind, or extreme emergency, consider using nitrate-reducing products like Seachem DeNitrate, or Seachem Prime, which can help lower nitrate levels in your aquarium.

Products and Tools

Here are some recommended products and tools to help in managing nitrate levels in your aquarium:

  • API Freshwater Master Test Kit: A comprehensive kit for monitoring ammonia, nitrite, nitrate, and pH levels.
  • Seachem DeNitrate: A filter media that promotes the removal of nitrates through anaerobic bacteria activity.
  • Seachem Pristine: A bacterial supplement that helps break down waste and reduce nutrient levels.
  • Seachem Prime: A water conditioner that detoxifies ammonia, nitrite, and nitrate, making it safe for aquatic life.

Conclusion

High nitrate levels in your fish tank can lead to a lot of health issues for fish, shrimp, and plants, or cause a ton of algae. Understanding the causes and implementing effective strategies is essential for maintaining a balanced and successful aquarium. Regular maintenance, appropriate filtration, lots of plants, and maybe the use of beneficial products will help you achieve optimal nitrate levels and ensure the well-being of your aquatic life.

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