How To Lower Nitrate Levels In A Saltwater Aquarium – 5 Ultimate Methods

Last Updated on February 14, 2022 by admins

How to lower nitrate levels in a saltwater aquarium? Click and find out the fastest and easiest methods to do so.

Nitrates are part of the nitrogen cycle that takes place non-stop. Unfortunately, things sometimes get out of hand, that is, nitrate levels jump up abruptly, bringing your aquarium into imbalance.

When faced with such a situation, many hobbyists wonder how to lower nitrate levels in a saltwater aquarium? Therefore stay with us and find out!

What Is Nitrate & Why Does It Occur?

Nitrate occurs as a by-product of the nitrogen cycle. This happens because fish food, waste, and other organic matter are broken down by bacteria which ultimately results in the formation of nitrates.

What Is Nitrate & Why Does It Occur

Learn more about: How to Make Fish Food Flakes?

Once it appears in your aquarium tank, one part can be further processed and converted to nitrogen gas and released into the atmosphere, but the vast majority actually remains trapped inside the tank.

As far as its form is concerned, nitrate appears in two forms, namely as organic nitrate (nitrogen that exists inside organic matter such as fish food, fish waste, algae, bacteria), and as dissolved nitrate (what is being tested).

According to some research, nitrate is not toxic to freshwater fish and invertebrates, but this is not applicable to marine fish and invertebrates, specifically corals. Also, it should be emphasized that nitrate itself is not as harmful, at least compared to toxic ammonia and nitrites. In any case, it is advisable to keep them under control.

Is There A Recommended Nitrate Level?

Recommended nitrate levels have changed over the years, and will certainly continue to change in the future. Generally speaking, saltwater aquariums should be kept under control, without stressing over a specific level. As long as filtration is working, you are feeding properly with an appropriate bioload, and you maintain the tank properly, elevated nitrates will not be a threat to your underwater world.

Many hobbyists recommend the use of the Redfield ratio, or the natural ratio of carbon: nitrate: phosphate found in our oceans. Most of them believe that the goal is to mimic this ratio in our tanks, to ensure that our pets get the nutrition they need.

The recommendations are as follows: 106 carbon: 16 nitrogen: 1 phosphorus. So, to conclude, 16 ppm of nitrate in your tank would require 1 ppm of phosphate to maintain a healthy environment. In terms of acceptable ranges, the acceptable range for fish-only tanks is 10-40 ppm, although there are cases with much higher levels with no adverse effects, and for reef tanks, it is 0.25 ppm, but not more than 5 ppm.

How To Measure Nitrate Levels?

The best possible option for monitoring nitrates is home water test kits. It is recommended to test for nitrates every 1-2 weeks or between water changes to monitor nutrient levels. Also, try to test nitrates and phosphates at the same time to make sure you keep both under control.

How To Lower Nitrate Levels In A Saltwater Aquarium?

Here are some methods you can use to lower your nitrate levels in a saltwater aquarium but keep in mind that none of this matters unless you take the time to solve the core of the problem.

Water Change Method

This is the quickest and easiest answer/option if you are wondering how to lower nitrate levels in a saltwater aquarium. By removing water that is contaminated with elevated nitrate levels and replacing it with quality water, you can (partially) solve this problem.

The thing is, changing the water alone usually won’t solve the original problem if you haven’t already located it. It serves only as a temporary solution, not as a final answer.

Chemical Additives

By using aquarium nitrate removal products, you can directly affect the problem but also affect some other chemical imbalances. Also, it is important to emphasize that chemical additives work great in tandem with a protein skimmer already working for your tank.

Nitrate Reactor Method

A nitrate reactor (or as it is often called denitrate reactor) is a device that helps to directly remove nitrate from aquarium water.

This type of system works on the principle of running low flow water through its system and depriving oxygen in its chamber, which ultimately results in the growth of bacteria that will consume nitrates in the water system. Pay attention that the nitrate level is lower in the reactor than in the main tank, as this means that your nitrate reactor is doing its part.

Refugium Method

Refugium is an additional chamber attached to the fish tank whose role, among other things, is to regulate the level of nitrate in your aquarium. You can also add a sand bed and living rock to it to help it act as an extra filter for your water supply.

Biopellet Reactor Method

A biopellet reactor is one of the most effective ways to lower nitrate levels in a saltwater aquarium, almost in the same range as changing water. The Biopellets are actually made of bacteria and as they break down, at the same time they reduce nitrate levels as water is pumped through the housing reactor.


One of these solutions alone probably won’t solve your problem, but careful planning and a combination of these methods certainly can. It is best to start with free and cheaper options and then move on to more expensive ones if needed.

The best way to ensure you have everything under control is by frequent water changes and regular testing. – Remember, prevention is better than cure!

Do you have any methods on how to lower nitrate levels in a saltwater aquarium? – Let us know in the section below!

Read more about How To Add CO2 To An Aquarium – The Easiest And Most Affordable Methods


What is the fastest way to lower nitrates in an aquarium?

The fastest way to lower nitrate in an aquarium is also the easiest - simply change the water. However, keep in mind that your tap water must have a lower level of nitrate than water in the tank. Only then will you be sure that your nitrate levels will drop. So, check the nitrate level in the tank as well as the tap to make sure you are doing the right thing.


What Reduces Nitrates In Reef Tank?

Here are the best ways to reduce nitrate in the reef tank:

Regular water changes,
Avoid overfeeding,
Rinse frozen food before feeding,
Increase the habitat of nitrifying bacteria,
Installation of refugium, bio pellet reactor and nitrate reactor.

Will A Protein Skimmer Reduce Nitrates?

Unfortunately, the answer is no! Protein skimmers don’t remove nitrates from the water. They remove the waste before it decomposes into nitrates, but they don’t extract nitrates from the water.