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Aquarium Nitrates; Lowering Nitrate Levels, How to Control
AQUARIUM OR POND NITRATES
Although much less toxic than ammonia and nitrite; Nitrate (NO3) as a nitrogen compound also causes stress at all levels making a fish’s organs work harder to adjust to their environment, especially at levels higher than 100 ppm).
The increasing stress results in the loss of ability to fight diseases, the ability to heal itself, and the ability to reproduce.
It is essential for you, the aquarium hobbyist, to maintain a proper environment for your aquatic companions.
High nitrate levels are often a sign of poorly maintained aquariums and will cause problems in the long term (I recommend levels under 40-50 ppm for FW, 20 ppm for Saltwater fish, & under 5 ppm or less for reef).
Nitrates are potentially dangerous due to the effects on the water chemistry and on a healthy environment for your fish while nitrates are accumulating.
The higher the nitrate levels, the higher and more severe the consequences due to the stress on your fish and the favorable conditions for a serious algae outbreak.
Nitrate levels around 5 ppm or less are found in nature which provides an almost nitrate free environment (although a Nitrate level of around 15 ppm is usually best for planted freshwater aquariums).
The higher the nitrate concentration the more stress for the fish. More severe stress is reached at levels exceeding 100 ppm. Many plants will fail before reaching this level.
Additional stress MAY be added due to an accumulation of life forms such as detritus worms feeding on decomposing waste, and the consequently higher biomass (organisms living in the aquarium) leads to an increasing demand of oxygen.
Reference: Aquarium Planaria? Actually Detritus Worms
I will also add that although nitrates are not dangerous in the short term unlike ammonia or nitrites; in established tanks I usually test this parameter more often as this is a good indicator of how well I am doing in my tank cleanings. Example; if enough water is being changed and with the correct frequency, as well as to whether additional nitrate removing products or procedures need to be employed. Tests of KH & GH are also useful in indicating an established tanks health.
Reference: Aquarium Cleaning; Reasons, Frequency, more
One more point about nitrate; I have tested the water on under sized aquariums /bowls containing otherwise healthy goldfish.
The nitrates would often exceed 200 ppm! These goldfish (although they appeared healthy), rarely lived more than 3-5 years as compared to the 12 + years of the goldfish I have kept for clients in pond and larger aquariums.
University studies in Cattle show nitrate levels in water over 221 ppm to be harmful or even fatal, so I sure would NOT want my fish kept at nitrate levels approaching this number.
*WHAT ARE NITRATES?
Nitrates (NO3) are compounds composed of a nitrogen and three oxygen atoms and are often the final stage in the nitrogen cycle of fresh and saltwater aquariums if there are not nitrate removing plants, algae, or nitrate reducing anaerobic bacteria present.
Nitrates are the conjugate base (chemical substance that releases a proton in the backward chemical reaction) of nitric acid (HNO3), consisting of one central nitrogen atom surrounded by three identical oxygen atoms.
The presence or production of large amounts nitrates can result in the presence of Nitric acid according to the Brønsted-Lowry theory of acids and bases which will in turn affect an aquariums pH and KH (which can result in dangerous pH swings).
For more about the nitrogen cycle, please reference:
*Aquarium Nitrogen Cycle
A high Bio-Load that often produces large amounts of organic mulm and decomposition in an aquarium (or pond) gravel or in filters is often a common cause of persistent nitrate problems.
Another clue to this is a pH that tends to drop quickly, often even with buffers added (assuming a higher new water pH); the breakdown of organic mulm or similar will lower pH while increasing nitrates.
Pockets of decomposing organics are often found in areas of deep fine sand, under rocks or other décor, or in large filters (especially canister filters).
*HIGH NITRATE DANGERS:
High nitrate levels which many sources based in human studies place as low as 30- 45 ppm of nitrate as harmful. The EPA recommend levels under 10 ppm in drinking water, although often this can higher especially in well water.
High nitrate levels can cause respiration problems in fish, lower or eliminate the ability to breed, resist disease, and lower activity of aquarium inhabitants.
In human studies high nitrate levels have been shown to dangerously lower blood pressure by causing the muscles that control the size of blood vessels to relax, this can be dangerous to fish too causing circulatory problems which can again result in poor disease resistance.
High Nitrate levels in aquariums will also result in high algae growths and in marine aquariums is toxic at even low levels to Cephalopods such as Octopus and to corals.
Another danger is in the bloodstream, nitrates can be converted biologically to nitrites, leading to "Brown Blood Disease".
For more on the dangers of Nitrates:
*Nitrates In Drinking Water
Temporary Relief of Nitrate Poisoning:
First, please note that high nitrates are not even close to the danger of high ammonia or nitrites for fish, so if these are the problem, high ammonia and nitrites should be addressed first.
Some have stated that moving from high nitrates to low nitrates or vice versa can also cause nitrate shock similar to pH shock, however this is anecdotal and my tests as well as research have yet to verify such claims (for one nitrates are NOT algorithmic like pH is).
*Medicated Baths using Methylene Blue can increase oxygen in the blood and quickly remedy ammonia, nitrite, and especially nitrate poisoning (in this order of effectiveness too with ammonia poisoning the least effective and nitrates the most effective).
See Reference: Performing Medicated Fish Baths, Dips, similar
*Spirulina Algae or Chlorophyll Remedy; these build the immune system and increase blood oxygen levels in fish that have suffered from nitrite or nitrate poisoning or oxygen deprivation. Spirulina is the better choice of the two, being much better at increasing immune function.
The most simple and effective way to administer Spirulina is via a high Spirulina based food such as Spirulina 20 or HBH Veggie/Spirulina Flake. Feeding Spirulina based foods although not a replacement for lowering your aquarium or ponds nitrate levels can be a reasonable albeit partial solution to chronic nitrate problems for many fish (not reef inhabitants such as Corals, Cephalopods, etc.).
If you have access to food grade Spirulina or Chlorophyll, these can also be used as a bath: Pre-mix 1 ounce of spirulina or chlorophyll per gallon of aquarium water (I suggest first liquifying the powder with sterile water to a make a liquid ounce); allow fish to soak for 15-30 minutes; perform this once or twice a daily. Use a fresh bath for each bath using your display tank water. This can be performed in 1/2 ounces with 1/2 gallon too for smaller fish.
Please read this article for more about Spirulina Algae:
Where to Purchase, Product References:
*Spirulina 20 Fish Food Flake
*HBH Veggie/Spirulina Flake
*Most importantly, follow the steps below to lower your aquarium or pond nitrates in the first place and often any possible nitrate poisoning issues will go away too.
*REMOVAL / PREVENTION:
Here are a few basics for removal/ prevention of nitrates (I will add to this list over time too)
- Water changes; for high nitrate levels changing as much as 60% then filling the aquarium only 80% (this cuts the nitrates in half), followed by a 50% change again which will then have an over all reduction of 75%. Also keep in mind to test your tap water as this can affect your nitrate levels as tap (& well) water often have some nitrates in the water already, I have tested as high as 25 ppm (although this is rare). So as an example you change 50% water that has 100 ppm with tap water that is 20 ppm you will not reduce nitrates by half to 50 ppm.
- Plants in Freshwater Aquariums (or ponds); Plants will keep lower nitrate levels. A well maintained planted aquarium maintains lower nitrates by more than one attribute:
- Direct removal of ammonia by some plants such as Hornwort (Foxtail), as well as removal of nitrates from the water column
- The roots also remove nitrates and other nitrogenous wastes.
- Often a well maintained sand, laterite, Plant Grower Bed, etc. around the roots maintain a healthy anaerobic filter bed without reverting to sulfide reduction (Hydrogen Sulfide production), which can often happen in freshwater aquariums where sand is used if no oxygen is allowed to permeate.
With a pond, nothing works better for nitrate removal from my experience than a Veggie Filter, which when constructed properly includes rooted bog plants along with a good de-nitrifying substrate, generally volcanic rock.
*Aquarium Plant Care, Information
*Hydrogen Sulfide Production in Anaerobic De-Nitrification for Aquarium/Pond Nitrate Removal
*POND VEGGIE/BOG FILTERS
- Vacuuming during most water changes of eventual nitrate producing mulm is essential for both freshwater and saltwater as long as this performed correctly so as to not disturb anaerobic bacteria in saltwater or plant roots in freshwater.
Please see this article: “Aquarium Cleaning”
- Lower you bio load/ DOC, as noted in the previous point about vacuuming high amounts of organic mulm/sludge that in turn leads to high DOC (dissolved organic compounds) in the water column is a major contributor of high nitrates. A strong indicator of this problem is a low pH and a KH under 50 ppm along with high nitrates (often over 80 ppm).
Check your filters (especially large capacity filers such as canister or large sump filters) for buildup of mulm/sludge. Under gravel filters can be a major contributors due to trapped decomposing waste under the plates and gravel, especially not cared for well Ornaments, decorative rocks and gravel can also trap copious amounts of decomposing organic waste.
Please also read this article:
Aquarium or Pond Bio Load
- Reduce Fish, this includes "Cleaner Fish" or similar; this is similar to the above recommendation as less fish or other inhabitants (crabs, shrimp, snails, etc.) means less organic waste.
As well I should address the often implied Urban Myth about "Cleaner Crews"; adding fish such as Plecostomus to clean your aquarium only cleans cosmetically. The facts are this fish or similar dumps far more organic waste than they take in and in fact while algae might be unsightly, removing it via a plecostomus not only removes a life form that removes nitrates, but adds a life form that adds much more to the nitrates. Snails are even worse in this respect.
I am not suggesting that fish such as Plecostomus should not be kept, but if you are keeping these (along with snails, both freshwater or marine) thinking these are keeping your tank bio load lower and thus nitrates lower, you have them for the wrong reason.
As an analogy; if you had a small child that is constantly spilling and making messes, would you "baby sit" this small child with your dog that is never let out? I think you would find the "Messes" eventually left from the dog to be just as bad and likely much worse.
- Reduce feeding and use foods that are more easily digested (made with amino acids that will be used by the fish/aquatic organism and not be expelled) such as Spirulina Algae based foods.
Your choice of food and over feeding can be a MAJOR contributor to DOC and in turn high nitrates, unstable pH, and low KH.
An excellent highly digestible line of fish foods is "Aqua Master" which includes probiotics in all their fish feeds and is used by many breeders of highly prized show fish.
Product Resource: Aqua Master Ultra Premium Fish & Turtle Foods
- In marine aquariums the use of "Live Rock", mud filters/Refugiums and/or protein skimmers can help reduce nitrates.
Mud filters and Refugiums remove nitrates while Protein Skimmers remove nitrogenous wastes (proteins) before they enter the nitrogen cycle. I personally feel some older style protein skimmers can be over rated due to the often erratic upkeep they require (although the newer models are often worth the expense in both effectiveness and lack of hassles).
I prefer the more natural use of live rock (as well as live rock crumbles in filters) and mud filters/Refugiums as well as Mangrove Plants and Caulerpa algae in my marine aquariums. Good deep sand (#00) beds of over 3” (with a ½” layer of #3 crushed coral on top for ease of cleaning) also are helpful as these allow anaerobic bacteria to form and remove nitrates.
Marine Aquarium Care, & Basics
Large Live Rocks which have now been popular in marine aquariums since the 1980s as decorations that also act as bio filters, are both a positive AND a negative, depending upon use.
Let me explain:
- An aged (seasoned) Live Rock specimen will have aerobic bacteria in the outer calciferous surfaces that remove ammonia and nitrites and anaerobic bacteria on the inner calciferous surfaces that remove nitrates.
- However often owners of new, unestablished saltwater aquariums will purchase Live Rock from a retailer that is NOT seasoned.
The results is this live rock is not so "live" and in fact has a lot of decaying material within the calciferous surfaces of the rock that instead raise ammonia, nitrites, and nitrates.
If your marine tank is well established and you add this unseasoned live rock (in increments), likely there will be no problem.
But if your tank is under 12 weeks of ages, I would urge the reader to inquire as to how long the retailer has had the so-called "live" rock; if under 8 weeks, do NOT purchase.
- The use of a Protein Skimmer.
In marine aquariums is an effective way (depending on the skimmer) of removing ‘protein’ based organics BEFORE they can enter the nitrogen cycle and thus become nitrates. These devices do NOT work in freshwater as they work via foam refraction which is a process that will not work in freshwater.
As well, there is also evidence that foam refraction will be limited by the use of carbon since carbon removes MBAS Foaming Agents.
See this article for more: Activated Carbon, Uses, Adsorption, Absorption.
For Reef tanks, these devices are almost a must, and generally the low end skimmers are not adequate, high end skimmers such as Warner Marine mesh wheel skimmer or the Tropic Marine V2 Skimmer are among two of many good choices.
Please see this article for more information about Protein Skimmers:
Marine Aquarium Protein Skimmers; Review
Product Resource: TMC V2 Skim; with Patented Venturi Injection System
- Use of NPX Bioplastics Nitrate & Phosphate Reducing Polymer Media
This is a top notch method for BOTH effective nitrate reduction as well as phosphate reduction (both of which when combined can be very detrimental to marine aquarium hard corals).
This is generally for MARINE aquarium use and it also requires a protein skimmer to be in use for best results. However use in a planted freshwater aquarium may be possible as some of the bacterial by-products may be assimilated into the plant root structures, as well the use of SeaChem Purigen may help further remove by products that may yellow the water (normally the use of Purigen in planted aquariums is not suggested, but with NPX Bioplastics this would be an exception).
While this product can be placed in any high flow filter, it is best utilized in a reactor or Fluidized Filter
Here is just one reference from a user of this VERY effective nitrate reducing product:
Where to purchase, product references:
*NPX Bioplastics Nitrate & Phosphate Reducing Polymer Media, By Two Little Fishies
*TMC Premium New Generation Fluidized Sand Bed Aquarium Filter
*SeaChem Purigen; Removes Water Yellowing Compounds
- "Vodka Method"
As with the above method, this is only for marine use and requires a Protein Skimmer. This method is also less exactly and simple with more issues with Gelbstoff which is a yellowing of the water and slime as a side effect, so the use of an Ozone Generator is also strongly suggested.
Where to purchase: TMC High Output V2 Ozonizer
That said, it is still an effective method for both nitrates and phosphates in marine reef aquariums.
See this excellent article for further information about this method:
- High Porosity Bio Media: I have had success in preventing this problem with the use of live rock crumbles in place of much of the standard bio filter media in saltwater aquariums so as to allow for de-nitrification deep inside these crumbles. Volcanic rock is a substitute that works well too for this and can be used in FW as well.
As to volcanic rock and live rock crumbles, the higher the flow rate, the larger the volcanic rock/crumble size so as to allow for correct anaerobic de-nitrification (generally about a ¾ to 1 inch diameter rock size for flow rates less than 350 gph).
Product Resource: Volcanic Rock Aquarium and Pond Filter Media
Another product I have used with good results, probably the best of these bio nitrate removing mediums, is SeaChem’s Matrix de-nitrifying bio media.
Eheim (Substrat Pro) and JBL (MicroMec) are similar products (in both cases, sintered glass) and are claiming larger specific surface areas than for Matrix, however there is a second consideration, and that is the size of the pores in the medium.
Generally, with very large pore diameters, we have smaller specific surface area, so that is not good. This generally rules out pores above 10 microns in diameter.
But we can go too far in the other direction as many products such as Eheim (Substrat Pro) and JBL (MicroMec) have done.
If we have a very large number of very, very small pores, then our specific surface area number will be phenomenal, but the medium will not work very well as a biological medium. This is due to physical limitations, specifically too small a volume to support bacterial growth, and the decreasing efficiency of fluid transport (necessary to carry nutrients to the bacteria and waste away from the bacteria) with very small pore sizes.
Regardless of which of the above de-nitrifying bio media you choose, these do NOT remove nitrates over night unlike chemical filter media such as Purigen, rather over time nitrate removing anaerobic bacteria form in these medias that slowly convert nitrates to free nitrogen (thus expelling the nitrogen to the atmosphere). Generally you need to allow 4 weeks plus to see measurable results, but once the results start these de-nitrifying bio media rarely need to be changed.
Where to purchase: SeaChem Matrix; High Porosity Bio Media
*Please note that many otherwise excellent bio media such as bio balls, bio stars, ceramic bio rings, etc., only perform nitrification, that is the conversion of ammonia and nitrites, but this only adds to nitrates as these products do NOT have the pore size and too much oxygen is available to the pores that are found on these products which oxygen in any quantity inhibits de-nitrification (the removal of nitrates).
- Macro-Porous Synthetic polymers, Ion Exchange Resins, Absorbents, etc.; there are several nitrate “sponge” or resins available, although these can be costly. Zeolite can be used in freshwater aquariums to remove ammonia before it ever goes thru the nitrogen cycle, eventually becoming nitrates.
API Bio-Chem Zorb Chemical Filter Media is an good example of a blended carbon and resins that can aid in nitrate control.
This is an excellent product for those who need more than just carbon, but do not have a serious nitrate problem.
Where to purchase:
*API Bio-Chem Zorb
Another excellent product is SeaChem’s Purigen which more effective for more serious nitrate problems than BioChem Zorb (althoug it does not contain carbon).
Purigen be used in both freshwater and saltwater and is specifically designed to be an organic scavenging resin.
Purigen generally ignores simple elemental compounds, having an extreme affinity for nitrogenous organics Purigen can also be regenerated with bleach, however do not use in combination with Stress Coat.
For more about this please read this article: Aquarium Answers: Aquarium Water Conditioners .
Purigen can also raise your Redox, so maintain a Redox balance with the use of additional minerals such as Wonder Shells.
Reference: Aquarium Redox, Balance, Potential, Reduction, Oxidation
Where to purchase, product resources:
*SeaChem Purigen Premium Synthetic Adsorbent
*Wonder Shells; Improves Mineral Cations, Redox Balance
- Organic Nitrate Reducing Products; such as Algone for freshwater or saltwater can aid in nitrate prevention/removal.
In fact in our aquarium maintenance companies controlled tests we found marked differences in aquariums (both freshwater and saltwater) in Nitrate levels between tanks with and without Algone Nitrate Controller.
Algone works by utilizing Nitrate fixating microorganisms which incorporate excess nitrogen into the cellular mass, while bio active enzymes assimilate nitrogen from the water column.
The concept (not the process) is similar to the use of a Marine Protein Skimmer, in that many nitrogenous wastes are removed without going through the nitrogen cycle. For this reason, I do not recommend using Algone in new tanks, only established fully cycled aquariums (as I would a Protein Skimmer).
Where to purchase: Algone for Nitrate Control, Water Clarifier in Aquarium
- Use a re-circulating micron cleaning filter so as to remove excess mulm/detritus from your aquarium without over cleaning (meaning excessive water changes over 50%) or in between regular water changes.
The Eheim Detritus Extractor Battery Gravel Vacuum is a useful device for this purpose as it removes many of the organics before they are converted via the nitrogen cycle to nitrates (similar in theory to a protein skimmer, albeit a very different process).
The key is this device (& similar devices such as the Vortex Diatom filter) efficiently removes fine organic particulates BEFORE they would otherwise go through the nitrogen cycle.
The use of this or similar recirculating filters/vacuums prevents the formation of nitrifying bacteria that would break down organics resulting in higher nitrates. The theory is similar as to how a protein skimmer works in marine aquariums, however this machine and similar can be used in salt OR freshwater!
Where to purchase: *Eheim Sludge, Detritus, Mulm Extractor Battery Gravel Vacuum
- Rinse filters often with de-chlorinated water to prevent mulm build up. This is especially important in “nitrate factory” filters such as Wet-Dry and canister filters.
The rinsing of sponge filters is also important. In heavily planted freshwater aquariums this is often not necessary as the plants will often consume most extra nitrates and over cleaning can actually reduce nitrates too low for heavily planted tanks with CO2. However in marine aquariums this IS essential.
This is especially important with canister filters and Wet/Dry filters which have the reputation within the saltwater side of the aquarium keeping hobby as “nitrate factories” due to the fact that these filters both trap a lot of organic debris and also are very efficient aerobic nitrifying filters yet do little for de-nitrification.
Rinsing bio media is helpful for these filters as well as increasing frequency of this procedure; this also applies to freshwater as well.
- The use of fine micron poly filter pads inside easy to access filters such as aquarium power filters (HOB) or wet/dry filters.
I would place these in easy to reach spots and NOT use them to replace the regular filters or sponges, rather place a piece in front of the existing filter. This pad needs to be rinsed every 1-3 days. How this works is this filter material will trap fine organic particles BEFORE going through the nitrogen cycle which would otherwise result in nitrates. The key is regular rinsing in CHLORINATED water so as to prevent the formation of nitrifying bacteria that would break down organics resulting in higher nitrates. This is similar to how the micron cartridges work (except on a much smaller and less efficient scale) in cleaning filters.
I recommend generic versions rather than the more pricy name brands which can be cut to fit
Product Resource: Generic Fine Micron Poly Filter Pads
The use of or micron socks, often employed in marine reef systems can achieve similar results and should be rinsed often as well for best results.
- Check your clean water source as I have tested Tap Water in excess of 20 ppm and some wells may also be high.
The use of “clean water” that already has moderate amounts of nitrates lessens the effectiveness of water changes. For SW the solution is simple, I recommend the use of Reverse Osmosis, DI (Distilled) or similar water for mixing all new saltwater and for topping off for evaporation.
For FW, this is a bit more difficult as RO/DI water is missing VERY essential elements for fish osmoregulation so its use is not generally acceptable (the use of marine salt mix replenishes ALL necessary elements back to the water). At best the FW aquarist can uses partial RO, DI or similar and then reconstitute the water with minerals with products such as Wonder Shells, Alkaline Buffers, and Cichlid Salts.
Recommended Further Reading:
Tap Water, Use in Fresh and Saltwater Aquariums
Where to purchase, product resources:
*TMC RO Aquarium Water Filter Systems
*SeaChem Marine, Alkaline for Fresh and Saltwater
*SeaChem Cichlid Salt, Minerals for most Freshwater Fish
- Carbon does not remove nitrates; although the use of carbon has its supporters and detractors, one aspect of activated carbon that is clear is that it cannot remove nitrates. Activated carbon filtration does not remove microbes, sodium, nitrates, fluoride, and hardness. HOWEVER Carbon can remove DOC, which eventually can lead to high nitrates, so the use of carbon in aquariums with nitrate problems is certainly a worthwhile endeavor.
Please reference the more in depth Aquarium Answers article about the use of carbon:
Aquarium Answers; Activated Carbon
Please reference this other Aquarium answers article for more other filter media types as well:
Aquarium Filter Media; Types, Capacities and more
Please reference this article for more about the production of Hydrogen Sulfides during the process of De-Nitrification: Hydrogen Sulfide production in anaerobic De-Nitrification for Aquarium/Pond Nitrate Removal
For a map of Nitrates in World Rivers, please click below
Nitrate Levels in Major World Rivers
For more referenced aquarium information pertaining to:
*Freshwater Aquarium Care, Basics to Advanced
*Saltwater Aquarium Care, Basics to Advanced
The article below is a MUST READ for anyone interested in moving from basic aquarium keeping to more advanced aquarium keeping, including better Redox Balance:
Other Recommended Reference & Product Sites
POND CARE INFORMATION; Complete Steps
*UV Replacement Lamps; Aquarium or Pond
For TRUE High Output, Hot Cathode, Low Pressure UVC Germicidal Bulbs, for aquarium or pond
AcroPower Amino Acids for SPS Corals
AcroPower supplies essential amino acids that corals need to build their skeletal architecture
*Sponge Filtration; Complete Information about the use of Sponge Filters in Aquarium or Pond
*FISH AS PETS
Fish as Pets with articles & commentary of Interest to the Aquarium Hobby
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