Nitrates in Shrimp Tank. How to Lower them.

Nitrates in shrimp tank

Nitrate occurs naturally in any shrimp aquarium and is constantly produced and consumed (lowered) through the processes of the nitrogen cycle. In water, the fate of nitrate is primarily determined by the processes of nitrogen fixation, nitrification, denitrification, ammonification, and decomposition of organic matter. Rates of these processes are affected by pH, temperature, and oxygen availability. 

Nitrates have wide-ranging effects in dwarf shrimp. Adverse effects observed in shrimp include: mortality, growth reduction, reduced feeding rates, reduced fecundity, reduced hatching success, lethargy, behavioral signs of stress, bent spines, and other physical deformities. In addition, the smaller is the shrimp the greater its sensitivity to nitrates.

Any shrimp breeder knows that (ideally) the nitrates level should be zero or at least never be higher than 20 ppm in the tank. However, in fact, safe levels of nitrates have not yet been established for the dwarf shrimp in science. What we think is a safe level, actually, is not completely safe! Unfortunately, in many cases, we do not see it until it is too late. Nonetheless, even then bad things happen to our shrimp, aquarists often do not completely realize what caused it.

I have read a lot of articles and watched a lot of videos where people repeat the same thing – nitrates are bad. Sure, they are bad, but why? The interesting thing is that nobody talks about this part. Everybody talks about the “bad” consequence skipping the details. Therefore, I started digging and this is what I have found out from different studies.

How do Nitrates Affect Dwarf Shrimp

In the nitrogen process, ammonium is converted into nitrite and finally nitrite into nitrate by various bacteria. While the ammonium and nitrite can be dangerous for shrimp, nitrate is first of all a non-toxic (almost) substance.

So, if it is a non-toxic substance why is it so dangerous?

The answer is – because of in vivo conversion.

The actual problem lies in the intake. Nitrate can accumulate in the shrimp tissue. Biologists studied nitrate accumulation in tissues of the shrimp and found that nitrate accumulated in muscle, digestive gland, stomach, heart, gill, hemolymph, midgut, and eyestalk by factors from 0.20 to 1.3 over the ambient nitrate concentration.

Approximately 5% – 10% of the total nitrate intake is converted to nitrite by bacteria in the stomach of the shrimp and accumulated in eyestalk. As a result, the higher is the level of nitrates in the water, the bigger is intake. As a result, it leads to higher nitrates concentration in the shrimp, thus the more problems there are going to be. In addition, in vivo conversion of nitrates to nitrites significantly enhances nitrates’ toxic potency.

Therefore, the real culprits here are nitrites, which are hiding behind nitrates.

Note: Some German sites about dwarf shrimp also mention that for successful molting, shrimp need enough iodine to form the molting hormone crustecdysone. An excessively high concentration of nitrates prevents the absorption of iodine by shrimp. As a result of this, too little molting hormones are formed and failed molts may happen. It will also lead to the death of the shrimp.

I have tried my best to verify this statement. I found and read reports about crustecdysone (ecdysterone) but I could not prove or disprove it.

How do Nitrites Affect Dwarf Shrimp

When nitrites accumulate in body fluids, they start oxidizing the copper of hemocyanin in shrimp to meta-hemocyanin (or methemoglobin).

So, it works this way.

Just as humans have hemoglobin in the blood, shrimp have hemolymph, which contains hemocyanin. In shrimp, the oxygen is taken up by the gills and transported by hemocyanin, the respiratory pigment of their blood.

As a result, the nitrite binds to hemocyanin, occupying the active site in place of oxygen and causing a transformation to meta-hemocyanin, which is unable to transfer oxygen to the tissues. For this reason, nitrite decreases the amount of oxygen available for tissue oxygenation. As nitrite oxidizes the copper of this pigment, it can cause anoxia, hyperventilation, and alterations in cardiovascular function, molting problems, and death.

Note: Dwarf shrimp need oxygen in their tissues for proper molting and they cannot get it because of nitrates/nitrates.

You can read more about “How Copper Affects Dwarf Shrimp” right here.

Acute and Chronic Nitrates / Nitrates Toxicity in Shrimp Tank

When it comes to toxicity levels, researchers usually refer to acute and chronic toxicity. There some studies about this matter and fish on the internet. Unfortunately, there have not been any studies regarding the shrimp.

Therefore, any numbers we have are the result of multiple and combined experiences of shrimp keepers.

According to the common experience, in terms of concentration, nitrates should never be higher than 20-40 ppm (acute toxicity) in shrimp tanks. This is an absolute red zone for the shrimp. It means that there is a high chance that shrimp are going to die pretty quickly unless something changes.

The other part of that is chronic issues. This happens when nitrate levels are elevated but not necessarily to the point where your shrimp all of a sudden start experiencing problems right away. In most cases, because aquarists do not see an immediate negative effect, they call it also a safe level. Is it really safe?

Why Nitrates Safe Level is not that Safe?

OK, but what about the safe level of nitrates you can ask?

Ammonia, nitrite, and nitrate are substances that generally do not reach high concentrations in the natural environment. Nevertheless, in high-density aquaculture systems like dwarf shrimp aquariums, nitrogenous compounds can reach relatively high levels.

According to some researchers, the survival of the shrimp exposed to nitrate at the safety level concentration was similar to that found in the control group (in a nitrate-free tank). However, the growth in weight and final biomass were reduced by nitrate exposure.

In this context, the weight gain of shrimp has provided a practical method to allow researchers to define sub-lethal effects caused by nitrogenous compounds in the shrimp.

Therefore, the “Safe level” approach may be misleading in shrimp keeping and breeding hobby.

Note: Actually, the same results were with ammonia concentrations. Even if the level of ammonia was not lethal, the species showed growth reductions between 12% and 36%. In addition, shrimp showed significantly reduced resistance to bacterial infection.

Another interesting fact is that shrimp had reduced inter-molt periods. In another article about the molting process of dwarf shrimp, I already wrote that the rate of growth is a function of both the frequency with which they molt and the size increase per molt. However, there was almost no increase in the growth rate of the shrimp under such conditions! Molting occurred only in response to stressful conditions.

How to Test Your Tank for Nitrates

API test kit nitratesI prefer to use an API master kit. It is a liquid test kit. It tests for ammonia, nitrite, nitrate, pH, GH, KH, etc. Personally, I strongly believe that if you are serious about being in the shrimp, fish, or snail hobby. You should get one of these test kits.  You can check the current price (link to Amazon).

  1. Take your test tube. There is a 5 ml line. Fill it up to the line.
  2. Take the bottle “Nitrites”. Shake it for a few seconds.
  3. Then you add in 10 drops from the bottle. It will turn yellow or yellow-greenish.
  4. Take the bottle “Nitrates”. Shake it for 30-40 seconds.
  5. Add 10 drops from the bottle.
  6. Put the cap back on the test tube and shake this tube for one minute vigorously.
  7. Wait 5 minutes
  8. Read the results.

Note: You need to wear gloves for safety.

Tip: If you have a hard time seeing the colors when testing the water, hold it against a white piece of paper.

How to Remove Nitrates from Shrimp Tank

Nitrates are part of the eco-system in any shrimp, fish, or snail tank. Therefore, you should not be really surprised to see them in the tank from time to time. Though, it does not mean that you should not do anything to remove or lower them. So what are the main ways to keep nitrates at an acceptable level?

1. Water changes

Water changesWater-change-aquarium will remove a lot of nitrates. Be careful and do not do big water changes or your shrimp can face other molting issues. In addition, you need to keep in mind that you are running a closed system and everything needs each other to balance it out.

Big water changes can break this balance. It is always a risk. Especially for shrimp because they do not like changes. They prefer consistency.

2. Aquatic Plants

Water-lettuceThis is another great way to reduce nitrates in the tank. Plants will consume nitrates. However, not all plants are equally effective against nitrates.

You will need to use floating and fast-growing plants (for example, Water lettuce, Duckweed, Frogbits, Hornwort, etc.). These plants use up nitrate as a food source. Anubius, Java fern does not grow very fast. Therefore, they will not pull out a lot of nutrients out of the water. If something is not growing fast, it does not need a lot of food.

However, plants need more than just food. They need light to be able to process that food. So, if you have got a dimly lit tank your plants will not be able to cope with nitrates. Because they do not have enough energy for photosynthesis.

Plants in a tank are not magic. Although this is just something, you can do to additionally to help your tank and have low nitrates.

Note: Actually most aquatic plants prefer ammonia. It is less energy costly to consume compared to nitrates. However, they will still consume nitrates as well.

Note #2: Floating plants can greatly benefit the shrimp tank. Because other than removing nitrates, their root systems are very complex, which allows for the powdered food particles (like Bacter AE) and biofilm to accumulate there.

3. Pothos plants

Pothos plantsSometimes aquarists use pothos plants to remove nitrates. These plants cannot be submerged, so most people just place the ends of the stems in water to root and grow the actual plant outside the tank.

Pothos roots take in nitrates the same way aquatic plants do. Some aquarists claim that they are even more efficient than aquatic plants.

Read more about it in my article “How to Use Pothos Plants in a Shrimp Tank”.

4. Algae

algaeIt will also reduce the nitrate concentrations in the shrimp tank. In fact, it can be a good marker for how much nitrate is in the tank. Unless you keep Amano shrimp and grow algae on purpose.

So, if you have got a lot of algae growth and you are having a really hard time controlling it, test your tank for nitrates.

5. Cycled filter media (Nitrate absorbing)

Seachem denitrate and MatrixNowadays, we have filter media on the market for all occasions. For example, Seachem de❊nitrate™and Matrix (link to check the price on Amazon) will take care of the nitrate very quickly. In addition, Since de❊nitrate or Matrix are all biological support media, they do not actually ever exhaust, but they can grow less efficient with use by pore clogging. Prefiltering the water before it passes through these products will extend its useful life.

6. Denitrators

Nintrateminus The contained particles promote the activeness of microorganisms, which feed on nitrate and break it down biologically. For example, Tetra NitrateMinus – Click to view on Amazon.

7. The best advice – Stop overfeeding

Nitrates are caused mostly by an excess of food and organic waste. Therefore, you need to check how much you are feeding the shrimp.

Use feeding dishes for better control.

Can Seachem Prime remove nitrates from the shrimp tank?

Seachem Prime does not remove ammonia, nitrite, or nitrate from the system. It simply binds with those compounds making them harmless to the inhabitants and still bioavailable to the beneficial bacteria.

Detoxification is not the same as removing it. It only provides detoxification for an emergency. Which allows you to put off on a water change until you have time to do it.

Can filtration remove nitrates from the shrimp tank?

No, it cannot. Your filters will not help you at all. The water can be amazingly crystal clear but it does not mean that it is free from nitrates.

The point is that the filtration system harbors bacteria and that bacteria use ammonia and nitrites (which are very toxic to the shrimp) and then produce nitrates and nothing is removing them from the tank. Unless you have got plants, algae or you are doing water changes, etc.

However, if you clean your prefilter before waste starts to break down, it will slow down the accumulation of nitrates. The more organics we remove the less time it is for nitrates to accumulate.

Vodka vs nitrates

Now, I have your full attention 🙂

I believe that this method can be used only if you are completely desperate and do not have any other ways to remove nitrates from the tank. I will repeat that this is only for desperate measures. Although, it is a pretty well-known method in the reef tank community. Unfortunately, there are not many cases when aquarists use it in freshwater tanks.

So be very careful and keep in mind that you have to use a protein skimmer. It is an absolute must! However, it will not suffice the purpose it was built for (in a freshwater tank).


As the product of nitrification, nitrates can accumulate in large quantities, especially in a closed eco-system like the aquarium. Thus, nitrates can cause a lethal or sub-lethal effect to dwarf shrimp.

The main toxic action of nitrate (through nitrite) is due to the conversion of oxygen-carrying pigments to forms that are incapable of carrying oxygen. Nitrate toxicity to dwarf shrimp also increases with increasing nitrate concentrations and exposure times. In contrast, nitrate toxicity may decrease with increasing body size, and environmental adaptation.

2 thoughts on “Nitrates in Shrimp Tank. How to Lower them.

  1. Thank you very much for this article. I believe my new 5 gallon tank has cycled. My one concern is that I am at 0 Nitrates. But it sounds like that might not be a bad thing. PH 6.6, Ammonia 0, nitrite 0. Planted tank.

    1. Hi Julie,
      Are you planning to keep Caridina species? Your pH is a little bit to low for Neocaridinas.
      Regarding nitrates … well, it depends on the goals. If we are talking about shrimp keeping, ideally, we should not have nitrates.
      However, for the planted tanks, nitrogen is needed to some degree, it is the plants’ food.
      Nitrogen deficiency may cause problems for the plants.
      I would recommend reading the article “How to Spot Nutrient Deficiencies in Aquatic Plants“.
      Therefore, we have to find this fine line where we can keep plants and shrimp happily together.
      Best regards,

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