The 7 Best Saltwater Aquarium Nitrate Reducing Products, According To An Aquatic Veterinarian

Best Overall

Seachem Purigen Organic Filtration Resin

$15 $12 at Amazon

SeaChem Purigen is a synthetic absorption resin made up of a macroporous polymer. It is our top choice since it is easy to use, can be reused and changes color as it absorbs various chemicals in the water, including nitrate. It comes as a bag of small beads, so it is recommended to be kept in a mesh bag or fluidized bed (see our recommendation for a fluidized bed below – link?). Some Purigen products come ready-to-go in a bag. It is more expensive, but you can get multiple uses out of one purchase, depending on how much material needs to be absorbed.

Purigen needs to be replaced regularly, but you will know when depending on the color of the material. Starting out white or off white, the polymer will change color depending on what is being scrubbed from the water. After the material is no longer white, it will need to be replaced or recharged. You may get a few uses out of one bag by recharging it in a mild bleach solution. Some hobbyists use Purigen instead of carbon and it will act similarly, deactivating any water-based medication added to your tank. Purigen is safe for use in both saltwater and freshwater systems.

_{Available Sizes: 100ml, 500 ml |  Gallons Treated: 1ml per 1 gallon | Longevity: 4 to 6 months (depends on bioload)}

Another Great Option

DrTims NP-Active Pearls for Nutrient Control

$39 at Amazon $34 at Chewy

Dr. Tim’s entire product line comes heavily researched and tested, including their Aquatic NP-Active Pearls. This product works by providing surface area for nitrifying bacteria and contains a polymer that absorbs nitrate and phosphate from the water. It is a more expensive product and needs to be housed in a fluidized bed or mesh container within the filter.

It is critical that these beads be placed in an area where you can see them. Dr. Tim’s Aquatic NP-Active Pearls will slowly degrade over time and will need to be replaced. It can take a few weeks for you to appreciate any visual difference in your algae levels, but your water quality testing will allow you to determine your most effective dose.

_{Available Sizes: 450 ml |  Gallons Treated: 150 gallons | Longevity: 6 to 9 months}

Best Budget

Seachem Denitrate

$18 $16 at Amazon View on Thehiddenreef.com

If you’re looking for a budget method to remove your nitrates, consider SeaChem Denitrate. These fancy rocks essentially provide anaerobic housing for denitrifying bacteria that break down nitrate into nitrogen gas. They are much slower acting than the other products listed in this review, therefore they may be better suited for a minor, long-term solution to higher nitrate levels.

For best results, SeaChem Denitrate media will require specific water flow. Water flowing too slowly over these rocks will lose its bacteria due to lack of food, but too high water flow can cause incomplete conversion to nitrate gas. It can take some fiddling with your water flow to have this media work correctly. If you already have live rock in your tank, this product works very similarly, but will come into more contact with the water if placed in a filter.

_{Available Sizes:  1.7 pounds |  Gallons Treated: 100 gallons | Longevity: Several years}

Best Long-Term Nitrate Reducer

Kolar Labs Bio-Pellets

$57 at Amazon View on Kolarlabs.com

Kolar Labs Metabolix Bio-Pellets are made with PHA resin and derived from corn. They are very safe for fish and invertebrates and can be used in both freshwater and saltwater aquariums. Since they are an inert resin, they require an area of high water flow in order to be most effective, most commonly in a fluidized bed. If you do not have a fluidized bed, they can be added to your filtration in a contained mesh bag but will not be as effective.

The Kolar Labs Metabolix Bio-Pellets are made to absorb both nitrate and phosphate which can greatly increase your algae levels. However, this product is one of the most expensive on this list and will need to be replaced overtime. Consumers note that when first added, these beads can make the water very cloudy. The manufacturer recommends soaking the pellets in tank water for 24 hours to prevent floating and remove the dust prior. Overuse of these pellets can cause the water to become cloudy, so it is important to keep an eye on how much you use.

_{Available Sizes:  10.58 ounces; 1 pound; 1.32 pounds; 5 pounds |  Gallons Treated: 1 cup per 50 gallons | Longevity: 4-6 months}

Best Filtration Pad

PENN-PLAX Nitrate Reducer Media Pad

$10 $8 at Amazon

For a fool proof method of nitrate removal, any aquarium owner can use the PENN-PLAX Nitrate Reducer Filter Media Pad. Like any other filter, this pad can be cut to the correct size of your filter and will absorb nitrates in addition to acting as a mechanical filter. It will become inactive over time, and it is recommended to be replaced every 4-6 weeks. Thankfully, this product is very inexpensive and costs less than a lot of filter media out there.

For best results, the manufacturer recommends rinsing the filter pad prior to adding it to your tank. Since you may be replacing this filter media often, it is recommended to keep another, non-reactive pad in your filter at all times that will remain in your system for the life of your tank. You will need a sturdy sponge, such as the Aquaneat Aquarium Bio Sponge, that can also be cut to any specific size.

If you want, you can also cut up this pad into small cubes and add it to your fluidized bed like many of the other products on this list. It will not break down like some of the other products, but will need to be replaced to keep up with its nitrate-binding capabilities.  

_{Available Sizes:  10 x 18 x 1 inches | Gallons Treated: Up to 50 gallons | Longevity: 4-6 weeks}

Best Nitrate and Phosphate Reducer

Red Sea NO3:PO4-X

$39 $37 at Amazon

Red Sea NO3:PO4-X is specifically designed to treat both nitrate and phosphate overload in coral tanks with algae issues. It can be used in other systems but was specifically designed for use in saltwater coral aquariums. Red Sea NO3:PO4-X works by providing additional supplementation for heterotrophic bacteria that utilize nitrogen and phosphate as a food source thereby naturally removing it from your system. However, with the supplementation of these bacteria comes a secondary bacterial bloom. Therefore, it is highly recommended to use this product with a protein skimmer to remove the additional proteinaceous bacterial load.

Keep in mind that the main active ingredient, ethanol, is highly flammable, so store this product in a safe place and keep it away from children. This product works very similarly to the “vodka method” to reduce nitrates. The ethanol in vodka also promotes bacterial growth for these hardworking bacteria.

_{Available Sizes:  16 ounces |  Gallons Treated: 1-3ml per 25 gallons | Longevity: Varies, check expiration date on label}

Best Bacteria

Dr. Tim's Aquatics One and Only Live Nitrifying Bacteria

$34 at Amazon $15 at Chewy

Nitrifying bacteria convert your fishes’ primary waste product, ammonia, into nitrate, as part of its biological filtration. There are many bacterial products available on the market claiming to “instantly start” your biological filtration by providing you with the bacteria necessary for your tank to survive. However, many of these claims are false and have shown in independent tests to be completely ineffective. It is just not that simple to drop a bacterial bomb into your tank and expect it to do all the heavy lifting.

Dr. Tim’s Aquatics One and Only Live Nitrifying Bacteria was the one product we tested in our hospital that actually shortened the cycling period of our brand-new systems. Rather than 5-6 weeks, the system we tried only took 4.5 weeks. Is it magic and will solve all your cycling problems? Absolutely not. Will it give your system and small and safe boost. Yes; just don’t expect miracles.

_{Available Sizes:  2, 4, 8, 16, 32, 64, 128 ounces | Gallons Treated: 10 ml per 10 gallons | Longevity: N/A}