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The 6 Best Phosphate (Po4) Removing Products

When it comes to aquarium maintenance, there are a number of possible water quality concerns that can be detrimental to your fish. Phosphate is a major cause of freshwater contamination and a common supplement for marine coral tanks in saltwater. It can also be created by the breakdown of surplus fish meal. Phosphate cannot harm your fish at high concentrations, but its secondary algal bloom can deplete oxygen and substantially change the pH. Due to the fact that algae need phosphate as a food supply, an increase in phosphate will result in a substantial rise in algal growth. BestForPets (bestforpets.org) has produced a list of the best phosphate (Po4) removing products for your convenience.


Best Overall: Seachem PhosGuard 1 Liter

SeaChem PhosGard is our top choice for phosphate reduction in aquariums because to its user-friendliness, effectiveness, and reasonable cost. It may be used in both freshwater and saltwater, however users have reported higher phosphate reduction outcomes in saltwater.

The particulate resin is not as fine as some of the other products, thus it must be well rinsed before being added to the system. There may be a brief exothermic reaction when you initially put it to your aquarium, but this will rapidly fade. Use it in locations with strong water flow and be prepared to replace it frequently if problems continue.


  • Simple to use
  • Affordable
  • Effective


  • Can heat when added to a tank.
  • Needs a rinse
  • Suggested storage in a mesh bag

Best Liquid: Brightwell Aquatics Phosphat-E

Liquid phosphate removers are optimal for temporary phosphate increases. In order to retain their efficacy for chronic conditions, you must regularly add them. Brightwell Aquatics Phosphat-E is designed only for saltwater aquariums, yet it is quite effective and comes with clear dosing directions based on the severity of your phosphate surge.

When the liquid has bound the free-floating phosphate, your water may become briefly hazy as the insoluble particles fall to the bottom. Following a thorough cleaning, your phosphates will be eliminated.


  • Simple to use
  • Affordable
  • Specific dosage recommendations


  • Must continue utilizing
  • May render water murky

Best Sponge: API PHOS-ZORB Aquarium Canister Filter Filtration Pouch

API’s Phos-Zorb is one of the most accessible and user-friendly sponge/resin phosphate removers on the market. It can be found in most large pet retailers and is simple to apply. It may be used in both freshwater and saltwater and will eliminate phosphate continually.

Little white spheres that serve as phosphate sponges are offered in pre-measured packages. It will also remove silicates from your water, so place it in a location with strong water flow. Sometimes, you will need to change your package; the manufacturer advises every two months, but your tank may differ.


  • Simple to use
  • Persistent phosphate binding
  • Affordable


  • Sometimes need to replace
  • Cannot alter packing to fit tank size

Best GFO: Two Little Fishies Phosban

The manufacturer of PhosBan is Two Little Fishies. These granules of synthetic ferric oxide hydroxide have a very high capability for absorbing phosphate from both saltwater and freshwater. Moreover, it adsorbs silicate and does not release adsorbate.


  • Permanent phosphate removal
  • Also eliminates silicates.


  • Performing best in reactor
  • Must be refilled often

Best Splurge: D-D Rowahos Phosphate Remover

If you want to go all out for your fish, D-D Rowahos Phosphate Remover is the most expensive option, but it is effective. It is a granular ferric oxide, therefore handling it without a mesh bag may be quite messy. It requires a high water flow rate to perform well, therefore place it strategically within your filtration system.


  • Extremely efficient


  • Fine particles
  • May be dirty, requiring regular replacement

Best Budget: Fluval ClearMax Phosphate Remover

Seeking a cheap and simple way to reduce your phosphate levels? Then a FLUVAL ClearMax Phosphate Remover sponge is required. These bags of resin, which are part of the FLUVAL filter product range, are most effective when used in conjunction with other FLUVAL filter products.

You can still use this product if you don’t have a FLUVAL filter, but you may have to be creative with its integration. It is effective in both freshwater and saltwater and has some capacity to remove nitrite and nitrate, but its strength lies in phosphate removal. The manufacturer suggests monthly replacement, although it depends on the phosphate levels in your aquarium.


  • Simple to use
  • Cheap


  • Not compatible with all filters
  • Often requires replacement

Buying Guide

There are three kinds of phosphate-removing products to consider: liquids, sponges, and granular ferric oxide (GFO). Liquid solutions are simple and straightforward to use, but they require frequent re-dosing. Sponges are also simple, but they must be replaced periodically. Some can be recharged in accordance with the manufacturer’s guidelines.

Granular ferric oxide employs a positively charged ion to bind and attract negatively charged phosphate ions. This will cause precipitation to settle on the water’s surface, resulting in brief cloudiness.

Method of Operation

Phosphate removers are either liquid additives, sponges or resins, or ferric oxide in granular form. All of these items are effective in sequestering phosphates, although their environmental effects vary greatly.

Dosage Directions

Depending on the product you choose, dosage might be either basic or complicated. Several of the goods chosen for this evaluation were superior than others on the market due to their straightforward instructions.

Consider how frequently you must add the product back to your system or replace it with new media. The product will likely provide some direction, but you may need to continue monitoring your levels to be certain.

How to Fill Up Your Tank

Unless you are using a liquid that disperses easily in any tank, the location of your GFO or sponge will affect its effectiveness. Both GFOs and sponges must be put in a location with a strong water flow, often within a filter component. Several of these goods might be messy, thus it is generally advised to store them in a mesh bag.


Does phosphate hurt fish?

Phosphate is not toxic to fish, however it will dramatically increase algal growth. In high concentrations, algae can suffocate your corals and consume all the oxygen in the water. Algae requires both phosphate and nitrate as a food source, so be sure to frequently check your levels and do routine maintenance to reduce your reliance on other treatments.

Exist products that eliminate both nitrates and phosphates?

There are a few treatments on the market that remove both nitrates and phosphates, but their effectiveness is diminished as a result. There are multiple ways for eliminating phosphate and nitrate from the body, and typically one works better than the other for a certain substance.

If you have persistent problems with both nitrate and phosphate, you should examine your maintenance routine and fishes’ food before adding any substance to your system.

Do protein separators eliminate phosphates?

Phosphates are not removed by protein skimmers. Phosphate reactors resemble protein skimmers in appearance but employ GFO material for efficiency. Phosphate cannot be removed by bubbling air through phosphate-containing water, as a protein skimmer does to remove proteinaceous particles.

Does phosphate remover eliminate algae growth?

Phosphate remover does not directly kill algae, but removes their food source. Algae thrive on the phosphate and nitrate created by your fish and their surroundings. Reduce food waste and apply a phosphate binder if you eliminate these organisms during routine maintenance.

Most phosphate binders can be used briefly to control surges until normal levels are restored. In the unlikely event that your source water is strong in phosphates, you may need to use a phosphate-binder for an extended period of time if you have significant algal problems.

How are phosphate levels measured?

It makes sense to purchase a phosphate test kit if you see that your algae is growing uncontrollably. Some test kits for freshwater may contain a phosphate test kit, although not many.

There are several low-cost liquid-based kits available in pet specialty stores and online. Bear in mind that some products, such as those generated with liquid products, may test positive for bound components until the precipitate is physically removed from the system.

How can I determine if my product is effective?

After the first few days of applying a phosphate remover, you should observe a reduction in algae growth. Phosphate is bonded to an insoluble substance that must settle out of the water, which may result in hazy water. With your test kit, you should observe a decline in phosphate concentration.

If you are not seeing results, carefully read your instructions. If you are not using a liquid product, place your media in an area with a strong water flow so that it comes into touch with more of the tank’s water.


SeaChem PhosGard is our top pick since it is user-friendly, inexpensive, and effective. If you are searching for a liquid phosphate remover, we recommend Brightwell Aquatics Phosphat-E; however, liquid phosphate removers are ideal for addressing temporary phosphate spikes. BestForPets (bestforpets.org) believes that our evaluations and guide will help you locate the best phosphate (PO4) removing products.

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Dr. Deborah Fletcher

Deborah R. Fletcher, DVM, is a skilled veterinarian with more than 15 years of experience dealing with companion and exotic animals. She has experience caring for a variety of animals, including household cats and dogs, reptiles, birds of prey, and even primates. Dr. Fletcher is a valuable part of the BestForPets team, where she contributes to their aim of providing pets and their owners with the finest possible treatment and services.

Veterinarian (DVM) Dr. Deborah Fletcher


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