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 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 pH. Elevated phosphate will dramatically increase your algae growth, since they use it as a food source.
If you are unable to resolve the issue through regular water changes, read on for the best phosphate removing products to help you out.
Best Overall: Seachem PhosGuard 1 Liter
Easy to use
Can heat up upon adding to tank
Requires a rinse
Recommend keeping it in mesh bag
Easy to use, effective treatment and reasonably priced makes SeaChem PhosGard our best overall pick for phosphate reduction in aquariums. It can be used in both freshwater and saltwater, although users have gotten better results in their overall phosphate reduction in saltwater. The particulate resin is not as small as some of the other products, but can use a good rinse before adding it to your system. You may notice a slight exothermic reaction when you first add it to your tank, but this will dissipate quickly. Use it in areas of high water flow and be prepared to replace it regularly for persistent issues.
Best Liquid: Brightwell Aquatics Phosphat-E
Easy to use
Clear dosing instructions
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.
Best Sponge: API PHOS-ZORB Aquarium Canister Filter Filtration Pouch
Easy to use
Continuous phosphate binding
Have to replace occasionally
Cannot manipulate packaging to suit tank size
Of the sponge/resin phosphate removers, API’s Phos-Zorb is easy to find in most major pet stores, and is easy to use. It can be used 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, which the manufacturer recommends every two months, but your tank may vary.
Best GFO: Two Little Fishies Phosban
Continuous phosphate removal
Also removes silicates
Works best in reactor
Needs to be replaced regularly
PhosBan is manufactured by Two Little Fishies. These synthetic ferric oxide hydroxide granules have an extremely high capacity for absorbing phosphate from saltwater and freshwater. Also, it adsorbs silicate and does not release adsorbed substances.
Best Splurge: D-D Rowahos Phosphate Remover
Can be messy, requires regular replacement
If you want to go all out for your fish, D-D Rowahos Phosphate Remover has the highest price tag, but gets the job done. It is a granular ferric oxide, so it may be a little messy if not contained within a mesh bag. It requires high volume water flow in order to do the best job, so be strategic when placing it within your filtration.
Best Budget: Fluval ClearMax Phosphate Remover
Easy to use
Doesn’t work with all filters
Needs to be regularly replaced
Want a cheap and easy method to bring your phosphates down? Then you need a FLUVAL ClearMax Phosphate Remover sponge. 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 may need to be a little creative about its integration. It will work in freshwater or saltwater and has some ability to also 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.
What To Look for in a Phosphate Removing Product
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 are also easy, but need to be swapped out occasionally. Some can be recharged following the manufacturer’s instructions. Granular ferric oxide utilizes a positively charged ion to attract and bind to negatively charged phosphate ions. This will cause a precipitate that will settle out of the water, causing temporary cloudiness.
Mechanism of Action
When looking at phosphate remover products, they will either be a liquid additive, a sponge or resin, or a granular ferric oxide. All of these products are effective at sequestering away phosphates, but will act very differently within your environment.
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.
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 regular maintenance to limit your supply on other remedies.
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 product than the other. If you are having continual issues with both your nitrate and phosphate, take a close look at your maintenance regimen and fishes’ 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 utilize GFO media in order 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 utilizes phosphate and nitrate produced by your fish and their environment to grow and flourish. If you remove these with your regular maintenance, minimize food waste and 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 your source water is high in phosphates, you may need to use a phosphate-binder long term with severe algae issues.
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 in order for it to come in contact with more of your tank’s water.
Why Trust The Spruce Pets?
With over nine years 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.