Is phosphate harmful to fish?

Phosphate itself is not harmful to fish, but it will significantly boost your algae load. Most of the time, algae is an aesthetic nuisance, but at high levels, it can choke your corals and suck all the oxygen out of your water. Algae uses both phosphate and nitrate as a food source , so be sure to check your levels regularly and keep up with your routine maintenance to avoid having too much of either.

Do any products remove both nitrates and phosphate?

There are a few products available that remove nitrates and phosphates, but in doing double duty, a product’s potency is reduced. There are different mechanisms for removing phosphate and nitrate from your system and often, one will work better for one than the other. If you are having continual issues with both your nitrate and phosphate, take a close look at your maintenance regimen and fish’s diet before dumping something else into your system for a quick fix.

Do protein skimmers remove phosphates?

Protein skimmers do not remove phosphates. Phosphate reactors look very similar to protein skimmers but use GFO media to be effective. Bubbling air through water containing phosphates, such as a protein skimmer does to remove proteinaceous material, does nothing to remove phosphate.

Does phosphate remover kill algae?

Phosphate remover does not kill algae directly but takes away their food source. Algae use phosphate and nitrate produced by your fish and their environment to grow and flourish. The best way to reduce phosphate and nitrate levels is to remove them through regular maintenance and minimize food waste, but in some cases, you may need to add a phosphate binder. Most phosphate binders can be used temporarily to take care of spikes until you get back to your normal routine. In the rare case that your source water is high in phosphates or you have severe algae issues, you may need to use a phosphate binder long-term.

How do you test phosphate levels?

If you notice your algae getting out of control, it makes sense to invest in a phosphate test kit. Some freshwater test kits may include a phosphate test kit, but not many. Many inexpensive, liquid-based kits are available in specialty pet stores and online. Keep in mind that some products may test positive for bound components, such as those created with liquid products until the precipitate is physically removed from the system.

How do I know if my product is working?

If you are using a phosphate remover, you should see a reduction in your algae load within the first few days. You may see cloudy water as phosphate is bound into an insoluble compound that will need to settle out of your water. Using your test kit, you should appreciate a drop in phosphate levels. If you do not see results, read your instructions carefully. If you are not using a liquid product, be sure to have your media in an area of high water flow for it to come in contact with more of your tank’s water.

Does vinegar remove phosphate?

Yes, vinegar can help remove phosphate, but the results happen very slowly and gradually over time because the removal is largely dependent on bacteria consuming the phosphate. For this reason, vinegar shouldn't be the primary method of removal for high phosphate levels.

Is adding chaeto (live algae) to an aquarium helpful for removing phosphate?

Adding chaeto to an aquarium can effectively reduce phosphate because the fast-growing macroalgae can efficiently absorb it, along with nitrates, from the water column, with the algae refugium acting as a natural filtration system.

The 7 Best Phosphate (PO4) Removing Products of 2025

A phosphate remover we recommend on a blue background — The Spruce Pets / Lecia Landis

When it comes to cleaning your aquarium, there are many potential water quality issues that can be problematic for your fish. Phosphate is a common source of water contaminant in freshwater and is a common additive for saltwater marine coral tanks. It can also be produced by excess fish food as it breaks down.

At high levels, phosphate cannot hurt your fish, but its secondary algae bloom can deplete oxygen and significantly alter your tank's pH. If you are unable to resolve the issue through regular water changes, phosphate-removing products can help you out.

Our Top Picks

Best Overall:

Seachem PhosGuard at Amazon $21

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Best Liquid:

Brightwell Aquatics Phosphat-E at Amazon $23

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Best Sponge:

SALE

API PHOS-ZORB at Amazon ~~$10~~ $8

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Best GFO:

Two Little Fishies PhosBan at Amazon $23

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Best Splurge:

D-D Rowahos Phosphate Remover at Amazon $50

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Best Budget:

SALE

Fluval ClearMax Phosphate Remover at Amazon ~~$18~~ $10

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Best Filter Pad:

EA Premium Phosphate Reducer Filter Pad at Amazon $10

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Best Overall

Seachem PhosGuard

PHOTO: Courtesy of Amazon

$21 at Amazon $10 $7 at Petco $61 at PetSmart

What We Like

Easy to use
Effective
Can be used in freshwater and saltwater

What We Don't Like

Can heat up upon adding to tank
Recommend keeping it in mesh bag

Easy to use, effective, and reasonably priced, SeaChem PhosGard is our best overall pick for phosphate reduction in aquariums. It can be used in both freshwater and saltwater, but it's more conducive to phosphate reduction in salt water.

The particulate resin granules are not as small as some other products that made our list, and we recommend giving it a thorough rinse before adding it to your aquarium system. You may notice a slight exothermic (heat-emitting) reaction when you first add it to your tank, but that should dissipate quickly. It should also be placed in areas of high water flow and replaced regularly for optimal results.

_{Water Type: Saltwater, freshwater | Container: Bag, tub}

Best Liquid

Brightwell Aquatics Phosphat-E

PHOTO: Source: Brightwell Aquatics

$23 at Amazon

What We Like

User-friendly
Clear dosing instructions

What We Don't Like

Have to keep using
Can turn water cloudy

Liquid phosphate removers are best for transient increases in your phosphate. For persistent issues, you must continually add them in order to maintain their efficacy. Brightwell Aquatics Phosphat-E is made for saltwater tanks only but is very effective, with clear dosing instructions depending on the severity of your phosphate spike.

Once the liquid binds the roaming phosphate, your water may be temporarily cloudy as the insoluble particles settle out. After a thorough cleaning, your phosphates will have been removed.

_{Water Type: Saltwater | Container: Bottle, tub}

Best Sponge

API PHOS-ZORB

PHOTO: Phos-Zorb

$10 $8 at Amazon $15 at Chewy

What We Like

Pre-measured doses
Continuous phosphate binding
Widely available

What We Don't Like

Have to replace occasionally
Cannot manipulate packaging to suit tank size

Of the sponge and resin phosphate removers, API’s Phos-Zorb is easy to find in most major pet stores, and it's easy to use. It's suitable for use in freshwater or saltwater and will work continuously to remove phosphate. It is sold as a pre-measured package containing small white spheres that work as a phosphate sponge.

It will also remove silicates from your water, so be sure to put it in an area of high water flow. You will need to replace your packet occasionally. The manufacturer recommends every two months, but your tank may vary.

_{Water Type: Saltwater, freshwater | Container: Bag}

Best GFO

Two Little Fishies PhosBan

PHOTO: Source: Two Little Fishies

$23 at Amazon View on Saltwateraquarium.com

What We Like

Continuous phosphate removal
Also removes silicates

What We Don't Like

Works best in a reactor

PhosBan is manufactured by Two Little Fishies in the United States. These synthetic ferric oxide hydroxide granules have an extremely high capacity for absorbing phosphate from saltwater and freshwater. They also effectively adsorb silicate and do not release adsorbed substances.

For proper use, PhosBan should be used with a PhosBan reactor, and it's suitable for ongoing control of phosphate levels.

_{Water Type: Saltwater, freshwater | Container: Bottle, tub}

Here Are the Best Internal Aquarium Filters, According to an Aquatic Veterinarian

Best Splurge

D-D Rowahos Phosphate Remover

PHOTO: Source: D-D Rowahos

$50 at Amazon

What We Like

Highly efficient removal of phosphates, arsenic, and silicates
Available in range of sizes to fit a variety of tanks

What We Don't Like

Fine particles must be handled with extreme care

The D-D Rowahos Phosphate Remover has the highest price tag, but it's highly effective for the removal of phosphates, arsenic, and silicate in saltwater. It is a granular ferric oxide, so it can be messy if not contained within a mesh bag. It also requires high-volume water flow in order to function properly, so handle it with care and precision when placing it within your filtration.

_{Water Type: Saltwater | Container: Tub}

Best Budget

Fluval ClearMax Phosphate Remover

PHOTO: Source: Fluval

$18 $10 at Amazon $6 at Chewy

What We Like

Straightforward instructions
Also removes nitrite and nitrate
Suitable for both freshwater and saltwater

What We Don't Like

Not compatible with all filters
Monthly maintenance required

The FLUVAL ClearMax Phosphate Remover sponge is moderately priced and the directions for use are straightforward. A member of the FLUVAL filter product line, these bags of resin work best when used in combination with other FLUVAL filter products. If you don’t have a FLUVAL filter, you can still use this product, but you may need to be a little creative about its integration.

It can be used in freshwater and saltwater and has some ability also to remove nitrite and nitrate, but phosphate removal is where it shines. The manufacturer recommends monthly replacement, but it will depend on your tank’s phosphate levels.

_{Water Type: Saltwater, freshwater | Container: Tub}

Best Filter Pad

EA Premium Phosphate Reducer Filter Pad

PHOTO: Amazon

$10 at Amazon

What We Like

Cut to fit any size
Traps debris underneath
Reduces phosphate levels
Helps keep water clear and free of algae

What We Don't Like

Raises pH level in freshwater upon initial introduction

The EA Premium Phosphate Reducer Filter Pad measures 18 by 10 inches and can be cut to fit any size filtration compartment in an aquarium using a standard pair of scissors. The filtration pad is made from resilient fibers that trap floating debris to effectively reduce phosphate levels in a tank. Plus, it's easy to use.

The thin filter pad is placed in the direction of flowing water, trapping debris and particulates as the water passes through. With use, the water in the aquarium will become more clear and free of algae.

The Phosphate Reducer Filter Pad from EA Premium can be used in saltwater or freshwater tanks, but it is likely to raise the pH level in freshwater at first, so use caution and monitor the levels before you place your fish back inside.

^{Water Type: Saltwater, freshwater | Container: Bag}

Final Verdict

SeaChem PhosGard is our Best Overall pick because it’s easy to use, affordable, and effective. If you’re looking for a liquid phosphate remover we recommend Brightwell Aquatics Phosphat-E, although liquid removers are best for fixing transient increases in phosphate.

What to Look For in a Phosphate Removing Product

Mechanism of Action

There are three categories you can look at when it comes to phosphate-removing products: liquids, sponges, and granular ferric oxide (GFO). Liquid products are easy and simple to use but require regular re-dosing. Sponges and GFO are also easy but need to be swapped out occasionally. Some can sponges be recharged following the manufacturer’s instructions. All of these products are effective at sequestering away phosphates but will act differently within your environment.

Granular ferric oxide works by adsorbing phosphate, which adheres to the surface of the GFO granules. Liquid phosphate removers bind to phosphate ions, creating a precipitate that settles out of the water and causes temporary cloudiness. Sponges filter phosphate out of the water, similar to the GFO adsorption process.

Dosing Instructions

Depending on the product you select, your dosing may be very straightforward or can be confusing. Many of the products selected for this review beat out others on the market because they had very clear instructions.

Also pay attention to how often you have to add the product back to your system or swap it out for new media. The product will likely give you some guidance, but you may need to keep testing your levels in order to know for sure.

Where to Put It in Your Tank

Unless you are using a liquid, which will disperse well within any aquarium, where you place your GFO or sponge will change how well it works. Both GFOs and sponges need to be placed in an area of high water flow, often within a filter component. Some of these products can be messy, so placing them in a mesh bag is frequently recommended.

FAQ

Is phosphate harmful to fish?

Phosphate itself is not harmful to fish, but it will significantly boost your algae load. Most of the time, algae is an aesthetic nuisance, but at high levels, it can choke your corals and suck all the oxygen out of your water. Algae uses both phosphate and nitrate as a food source, so be sure to check your levels regularly and keep up with your routine maintenance to avoid having too much of either.
Do any products remove both nitrates and phosphate?

There are a few products available that remove nitrates and phosphates, but in doing double duty, a product’s potency is reduced. There are different mechanisms for removing phosphate and nitrate from your system and often, one will work better for one than the other. If you are having continual issues with both your nitrate and phosphate, take a close look at your maintenance regimen and fish’s diet before dumping something else into your system for a quick fix.
Do protein skimmers remove phosphates?

Protein skimmers do not remove phosphates. Phosphate reactors look very similar to protein skimmers but use GFO media to be effective. Bubbling air through water containing phosphates, such as a protein skimmer does to remove proteinaceous material, does nothing to remove phosphate.
Does phosphate remover kill algae?

Phosphate remover does not kill algae directly but takes away their food source. Algae use phosphate and nitrate produced by your fish and their environment to grow and flourish. The best way to reduce phosphate and nitrate levels is to remove them through regular maintenance and minimize food waste, but in some cases, you may need to add a phosphate binder.
Most phosphate binders can be used temporarily to take care of spikes until you get back to your normal routine. In the rare case that your source water is high in phosphates or you have severe algae issues, you may need to use a phosphate binder long-term.
How do you test phosphate levels?

If you notice your algae getting out of control, it makes sense to invest in a phosphate test kit. Some freshwater test kits may include a phosphate test kit, but not many. Many inexpensive, liquid-based kits are available in specialty pet stores and online.
Keep in mind that some products may test positive for bound components, such as those created with liquid products until the precipitate is physically removed from the system.
How do I know if my product is working?

If you are using a phosphate remover, you should see a reduction in your algae load within the first few days. You may see cloudy water as phosphate is bound into an insoluble compound that will need to settle out of your water. Using your test kit, you should appreciate a drop in phosphate levels.
If you do not see results, read your instructions carefully. If you are not using a liquid product, be sure to have your media in an area of high water flow for it to come in contact with more of your tank’s water.
Does vinegar remove phosphate?

Yes, vinegar can help remove phosphate, but the results happen very slowly and gradually over time because the removal is largely dependent on bacteria consuming the phosphate. For this reason, vinegar shouldn't be the primary method of removal for high phosphate levels.
Is adding chaeto (live algae) to an aquarium helpful for removing phosphate?

Adding chaeto to an aquarium can effectively reduce phosphate because the fast-growing macroalgae can efficiently absorb it, along with nitrates, from the water column, with the algae refugium acting as a natural filtration system.

Why Trust The Spruce Pets?

With over nine years of experience in aquatic veterinary medicine, Jessie Sanders, CertAqV, knows all about the continual battle for a clean tank and what owners can do to correct it. Her background working in a major aquarium shows how large these issues can get and the correct set of steps to effectively resolve these issues.

Dr. Sanders is also the owner and chief veterinarian at Aquatic Veterinary Services, a mobile all-aquatic veterinary practice serving California and Nevada. Dr. Sanders is one of the first Certified Aquatic Veterinarians through the World Aquatic Veterinary Medical Association. Her exceptional veterinary practice serves pet fish, including koi, goldfish, bettas, cichlids, and more, and aquaculture facilities. Dr. Sanders is a Level II USDA Accredited Veterinarian and has been practicing for over seven years.

The Spruce Pets uses only high-quality sources, including peer-reviewed studies, to support the facts within our articles. Read our editorial process to learn more about how we fact-check and keep our content accurate, reliable, and trustworthy.

Kim E, Yoo S, Ro HY, et al. Aquatic toxicity assessment of phosphate compounds. Environ Health Toxicol. 2013;28:e2013002. doi:10.5620/eht.2013.28.e2013002