Common Problems from Having Too Many Nitrates in Your Aquarium and How to Avoid Them

January 25, 2021
January 25, 2021 Phil Overton

Although nitrates are not as harmful to your fish as the preceding nitrogen cycle components, ammonia and nitrite, they can harm your fish when allowed to accumulate in numbers that are too high for your fish to withstand. For this reason, this article will cover “common problems from having too many nitrates in your aquarium and how to avoid them.” In addition to explaining all the different ways you can avoid the nitrate spikes in your aquarium, this article will also cover some ways to remove the nitrates if they are climbing too high.

Closeup image of the Rio Grande Cichlid seen from the side

Problems with algae

Education of chlorella under the microscope in Lab.

One of the common problems you might see in your aquarium if the nitrate level is too high is an overgrowth of algae, otherwise known as an “algal bloom,” which can have negative effects on the balance and health of the tank’s ecosystem if it gets out of hand. Because nitrates are an essential component in the health of plants and act as fertilizer, having a too-high level of nitrates can promote quicker algae growth, which can—other than pose a cosmetic issue by turning the tank green—deprive the tank of oxygen. A little algae is fine and can even signify that your tank is healthy, but it can also become a problem if the algae grows faster than the tank chemistry can balance things out. In this case, you might notice the oxygen level drop so low the fish could become ill or die.

Problems with fish health

Many different factors can lead to issues with your aquatic pets’ health, and as mentioned in the introduction to this article, nitrate are not the only hazardous byproduct of the nitrogen cycle. Ammonia and nitrite are far more hazardous to fish, but high nitrates will also cause issues with fish health. Here are some of the health issues you might notice if your nitrate levels are too high for your particular tank and choice of fish.

Freshwater aquariums

Fish in freshwater aquariums can typically handle higher amounts of nitrate; you might see them thrive in tanks with 40 or 50 parts per million (ppm), and in some cases, even higher. Beta fish, for example, can withstand an extremely high level of nitrate, which is why can survive in small containers. But at some point, all fish—when their tank reaches nitrate levels higher than the species can survive—will start to demonstrate signs of illness, like fading colors or split fins, since the unfavorable tank conditions can leave your pets more susceptible to disease.

aquarium tank with different freshwater fish pets. neon tetra, angelfish and anothers.

In many at-home aquariums where the tank isn’t maintained properly, nitrates will slowly build up over time. It’s common for hardier fish to adapt to the higher nitrate levels if they increase so slowly that the fish is able to acclimate to the higher nitrate counts over time, but it isn’t recommended to let this happen. Many aquarium owners might think the tank is well balanced because the fish look healthy, but if the nitrate levels have climbed and new fish are added to the tank, the sudden nitrate level change to the newer fish will be a shock to their system, and chances are they won’t live long.   

Saltwater aquariums

Fish in saltwater tanks tend to be more susceptible to high nitrate levels, so you typically want to keep nitrates lower in your saltwater tank. The limits will vary depending on which types of fish you have, but some will recommend keeping the nitrate levels below 20 ppm. Sharks, for example, can have a difficult time staying upright, and other fish might show symptoms of disease much like the fish in freshwater aquariums, like split fins and faded color.

Coral reef aquariums

When creating the appropriate habitat for corals in a saltwater tank, it’s important to keep nitrates as low as possible—typically below 5 ppm. The level of nitrates can, as with other tanks, affect the organisms’ health, and with coral, this is often gauged by the vibrancy of its color. As the nitrates lower the levels of dissolved oxygen, the oxygen-deprived coral will noticeably fade. It can be tricky to keep the ideal balance, however, as corals do need some nitrates to survive. Some of the highly effective filtration media will get the nitrate levels to undetectable levels, and in that case, you might need to compensate by adding them back in, which can make it easier to control the levels.  

Clown Fish at Coral Reef Tank Underwater Aquarium

How to avoid high nitrate levels in your aquarium

One of the best ways to keep your tank properly balanced and fish happy and healthy is to avoid letting the nitrates in your tank get out of hand in the first place. Here are some ways to make sure to keep the nitrate levels in your at-home aquarium in check:

Don’t overfeed your fish

Overfeeding is a common issue with at-home aquariums, and this if often because people are surprised at how little food some fish truly need. Be sure to get familiar with the amount of food your aquatic pets require, as the amount will vary from species to species. Any uneaten food will settle to the bottom of the tank and rot, which will cause a spike in ammonia, then nitrite, and then into nitrate, causing a buildup that can quickly escalate to dangerous levels for your fish.

Don’t overstock your tank

Overstocking your tank (which, depending on the types of fish you have, for fresh water, can be more than one to two inches of fish per gallon of water) increases the number of organisms and need for food, which will increase the amount of organic matter breaking down in the tank. In addition to having more organic matter breaking down and eventually turning into nitrates, there are more fish breathing in the tank, which will increase the level of ammonia, adding to the nitrogen cycle as well. Without the proper maintenance and filtration, this will tax the ecosystem until it can’t process the excess biological matter, allowing nitrates to build up. Using the proper biofilter media can allow for higher tank stock levels as discussed in the section below.

Provide both aerobic and anaerobic bacteria places to thrive, to fully complete the nitrogen cycle by using high performance bio-filter media

Most aquarists know that it’s important to provide surfaces for beneficial bacteria to grow, such as with bio-balls and other types of bio-filtration media. But the thing that will help an at-home fish tank even more is providing the right kind and amount of surface area for both aerobic and anaerobic bacteria, which many fish owners overlook. These bio-filtration media will have deeper recesses, providing region where low-oxygen water can exist, such as in live rock or MarinePure® Bio-Filter Media, which have lots of small nooks and crannies deep enough for the oxygen-less bacteria to thrive in. These are the bacteria that will ultimately convert nitrates into nitrogen, a harmless gas that will release from the tank into the atmosphere. Some well set up systems can become so efficient at removing nitrates, that the nitrate levels can approach zero.

Clean out dead organic matter

Dead plants and livestock will add to the nitrogen cycle in a way that is similar to overfeeding. If a plant or fish dies in the tank and isn’t removed, that’s going to increase the amount of biological matter breaking down, which will cause an ammonia spike, and eventually a hike in nitrates. Because anaerobic bacteria take longer to proliferate than aerobic, chances are the system could be overwhelmed for a while.  

Cleaning the soil in the aquarium with a siphon

Be mindful of nitrates in source water

There is a possibility that nitrates can be found in the source water. If the tank still has a high amount of nitrate after its regular water change and cleaning, check the level of nitrates in the water source. Some people recommend using distilled or filtered water, but the most important thing to keep in mind is the water needs to be chlorine-free, as the chlorine will kill all the bacteria in the tank.

How to remove nitrates from your aquarium

Even though the best way to manage nitrates in your tank is to keep up with regular maintenance and avoid letting levels climb by implementing the methods mentioned above, if you do see the level of nitrates in the tank start to climb toward a level you’re not comfortable with for your specific tank, here are a few things you can do to reduce them while your tank finds its equilibrium:

Perform routine water changes

One of the primary purposes for changing an aquarium’s water is to lower nitrate levels. Aquarist will typically change out 10% to 20% percent of the water two weeks or so in an established system. Smaller, more frequent changes are easier to preform doesn’t cause a shock to the system. This can vary depending on the type of fish you keep, how well your tank is maintained, and what type of filtration media you’re using.

Add nitrate-reducing plants

Since plants use nitrates as fertilizer, adding them to your tank is one of the ways you can reduce the nitrate level in your tank. Some people will also keep a side tank or refugium to grow a hardy type of algae called chaeto (Chaetomorpha linum) that will also help keep the nitrate levels in check. Just make sure to remove any dead plants, as they can reverse any nitrate-removal progress you’ve made.

Green planted large tropical fresh water aquarium with small fishes in low key with dark blue background

Use a protein skimmer

Protein skimmers can be added to your tank and will remove the proteins before they can break down to ammonia. They are cylindrical shaped chambers that trap the proteins in the tank, which then turn into a brownish foam that can be emptied and cleaned out. This will help eliminate any excess buildup of proteins and other organic matter, like fish waste, dead plants, and uneaten food.   

Add high performance Bio-filter Media

If you keep experiencing high nitrate levels, you might want to look at your filter system, and the type and quality of the bio-filter media.  Medias such as MarinePure® will allow for anaerobic bacteria to develop which will reduce nitrates to nitrogen gas.  If this is the first time using such media in you tank, be patient, because the anaerobic bacteria can take several months to fully develop. Last line – If this is the first time using such media in you tank, be patient, a small tank with just a few inhabitants will mature at a very different rate than a large tank that if full stocked, bacteria growth is based on the food source available and the space allotted.  Anaerobic bacteria can take several weeks to several months to fully develop.

Learn More about CerMedia and MarinePure®

MarinePure Block

MarinePure GEMS

CerMedia LLC, located in Buffalo, New York, manufactures MarinePure® Bio-Filter Media, which is a man-made ceramic bio-filter media that has the unique combination of a large amount of surface area for beneficial bacteria to grow in addition to a network of open-flow pores. These features enable water to move easily throughout the part, allowing the nitrogen components to find the bacteria, allowing all parts of the nitrogen cycle to take place, including ammonia and nitrite elimination and nitrate reduction.  With MarinePure biofilter media, stocking levels can be increased and water changes can be reduced, saving time and money.

If you have any questions about how to access MarinePure® Bio-Filter Media or incorporate into your new or current tank, feel free to reach out to us. We’d love to help walk you through how to use this bio-filter media for a cleaner, easier-to-manage fish tank.

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