3 Best Phosphate Remover for Freshwater Fish Tank

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Phosphate (PO4) is a chemical compound present in all aquariums. It’s a natural source of phosphorus, one of the most abundant minerals on Earth.

It plays an important function in plant growth and metabolism. It can also impact the water quality in the aquarium.

You need to maintain a healthy balance if you have a planted tank. You don’t want too little or too much of this chemical.

How much is too much, and why should you worry about it? Keep reading to find out!

I’ll cover everything you need to know about the ideal phosphate concentration, its effects in the aquarium, what causes phosphate buildup, and how to get rid of excess phosphates.

What Causes High Phosphate in Fish Tanks?

There’s always going to be some phosphate in the tank. A little bit of this molecule goes a long way to help aquarium plants thrive.

Levels between 0.5-1.0 ppm or mg/L provide freshwater plants with all the nutrition they need to grow and stay healthy. Of course, you can have too much of a good thing too.

High phosphate levels can negatively impact water chemistry and cause algae blooms. It’s worth getting familiar with the most common causes of phosphate spikes in the aquarium so you know how to avoid these issues in the future.

There are two main sources of phosphate in aquariums:

– Indirect sources of phosphate:

The most common causes of high phosphate are indirect. In such cases, phosphate doesn’t get introduced into the tank.

It appears due to decomposing organic material (uneaten fish food, dead plant matter, fish waste). Keeping the aquarium and filter clean will help get the phosphate levels in check.

– Direct sources of phosphate:

Less commonly, aquarists might bump up the phosphate concentrations directly.

Replacement water, water conditioners like pH buffers, aquarium salts, fertilizers, and even some carbon filters may all contain high concentrations of phosphorus or phosphate.

Using these frequently may result in excessive phosphate concentrations, even in planted tanks.

Best Phosphate Remover for Aquarium

The ideal level of phosphates depends on your aquarium setup. Do you have lots of plants?

Then you might want to keep a phosphate concentration of at least 0.5 ppm. If you have no live plants in your tank, phosphate levels below 0.2 ppm are best for algae prevention.

Whatever your goal, you know it’s time to do something about it when there’s excess phosphate in the tank.

Too high levels won’t help the water quality, and your fish will feel these negative changes. Ideally, you want the level to be up to 1.0 ppm or lower.

Luckily, you have a few options to get rid of PO4 in your aquarium.

Seachem PhosGuard

Seachem has some of the best water treatments on the market, and PhosGuard is no different.

This product is easy to use and offers excellent value for your money. Each tub contains one kilogram or 2.2 pounds worth of product, which will last you a while.

PhosGuard looks very similar to organic filter media. It’s made up of granulated aluminum oxide beads, which are highly porous.

The texture and material make this filter media highly chemically active and give it an excellent absorptive capacity.

Its properties make PhosGuard the perfect choice for removing phosphate and silicate from the water column.

You need just 1/3 of a cup per 50 gallons. You put the beads in a filter bag, and the filter does all the rest for you. With the right dose, the phosphate levels should gradually drop to 0.2 ppm over four days of use.

You can leave the PhosGuard in the filter a while longer if the phosphate levels remain within acceptable limits.

This product won’t leak the PO4 back into the water, even when it reaches full capacity.

Fluval ClearMax

Fluval ClearMax is a chemical filter media made of premium-grade resin. It looks like gravel and comes in three 3.5-ounce packs.

The pre-packaged nylon bags make for easy access, use, and removal of filter media.

This product does a stellar job of removing phosphates from the water. But it doesn’t stop there! Fluval ClearMax also removes nitrites, nitrates, and odors, helping you maintain crystal-clear water and reducing aquarium maintenance needs.

The bags need replacing every month for best results so you can get good use out of this product.

Bags are sized 6” X 4.7” X 0.9”, so they’re best suited for sump and canister filters. But you can easily make them work in most other filters.


This filter media has the smallest grain of all the products so far. It looks like dark soil or fine gravel and is made of ferric hydroxide.

ROWAphos is among the best-rated phosphate-removing filter media. It has an absorptive capacity of 25 grams of phosphate per kilogram. But it can do so much more.

This product will also rid your aquarium of silica, arsenic, and other heavy metals and pollutants.

This product offers accessible multi-purpose chemical filtration and is equally suitable for freshwater and saltwater aquariums.

A 100-gram dose will help you remove as much as 3 ppm of phosphates from a 200-gallon freshwater tank.

The product recommendations state to use this filter media between two layers of filter wool. This product is also best suited for canister filters and should be used in small doses and replaced regularly.

If you plan to use this product, you can buy packages of as little as 3.5 ounces or up to 2.2 pounds.

Downsides of High Phosphate in Fish Tank

Phosphate is necessary for planted freshwater aquariums. It provides important nutrients to support plant growth.

Phosphate is not directly harmful to freshwater fish, even at concentrations above 1.0 ppm. So, why would you want to keep phosphate concentrations down, then?

Well, there are a few good reasons for this. Although not harmful in itself, high phosphate could cause other issues in the tank:

– Algae blooms

Algae need phosphorus to grow, so an excess of phosphorus in the tanks will encourage them to multiply rapidly.

Even worse, high concentrations of phosphate and nitrogen may also promote the growth of toxic blue-green algae (cyanobacteria).

Whether it’s cyanobacteria or any other strain of algae blooming in your tank, this is a serious issue.

Left unchecked, algae blooms can further degrade the water quality and negatively impact the health of your fish and live plants.

– Reduced oxygen concentration

As I’ve already mentioned, high phosphates encourage algae growth. Algae blooms are bad for multiple reasons, not just aquarium aesthetics or smell.

These micro-organisms can impact water quality in surprising ways, including by lowering oxygen.

Excess algae starve the water of oxygen, making the aquarium inhospitable for your fish.

As oxygen levels drop, the fish lose their appetite and become lethargic. If left unchecked for too long, hypoxic conditions can even kill fish.

– Poor water parameters

Water parameters are important for your fish. You need to maintain the right pH, temperature, hardness, and salinity, so your fish are comfortable and healthy.

And these parameters vary from species to species.

Excess phosphate can alter water chemistry. In freshwater tanks, most phosphates come in the form of H2PO4.

High phosphates thus result in a higher concentration of hydrogen molecules in the water.

This molecular makeup means that phosphates will make the water more acidic.

You’ll get a drop in pH and water hardness, which may be stressful or unhealthy for your fish.

– Stunted growth and nutrient deficiencies in plants

Aquarium plants need various nutrients to grow, including phosphate. Phosphate is a crucial nutrient. Without it, your plants wouldn’t thrive.

But excess phosphate might have the opposite effect. Too much PO4 can inhibit the absorption of nitrites, nitrates, CO2, iron, copper, and zinc.

The resulting deficiencies will impact plant growth, appearance, and health. To avoid such issues, it’s best to maintain a tight nitrate-to-phosphate ratio of 10:1. For every one-part phosphate, you should allow ten parts of nitrates.

Note that if the phosphate levels are already high, increasing the nitrates will raise toxicity risk in fish.

Do Live Aquarium Plants Remove Phosphate?

Live aquarium plants help stabilize water chemistry by removing CO2, nitrates, nitrites, ammonia, and, you guessed it, phosphates.

If your phosphates are lightly elevated, adding some green to your tank is an effective and natural solution.

Phosphate, alongside nitrogen and potassium, is one of the three primary macronutrients for plant growth. This means that plants will consume a lot of it to fuel their metabolism and growth.

The more plants you have in your tank, the higher the total phosphate consumption. Fast-growing plants also require more phosphate than smaller plants.

Phosphate is necessary to absorb other macro and micro-nutrients, especially nitrogen. Plants also use phosphate to form new cell structures and to photosynthesize light.

Unlike micronutrients like iron, manganese, and zinc, plants use phosphate constantly and in large quantities.

If there’s no phosphate in the aquarium, the plants won’t grow or absorb nutrients as well.

Signs of phosphate deficiency include stunted growth, darkened leaves, and loss of older leaves.

Because micro and macronutrient absorption is phosphate-dependent, a phosphate deficiency might co-occur with other deficiencies.

Does Pothos Remove Phosphate from Fish Tank?

Although it isn’t a traditional aquarium plant, the humble Pothos is gaining popularity as a novel tank decoration.

There are a lot of good reasons to add Pothos to your tank. This houseplant provides excellent nitrate and phosphate control.

It’s also hardy, fast-growing, and easy to use when aquascaping.

Pothos plants grow at an amazing rate of 12-18 inches per month. Given its rapid development, this plant soaks up tons of phosphate, nitrates, and other nutrients from the water.

The high nutrient uptake also makes Pothos an excellent form of algae control. Just remember this if you have other plants in your tank.

Without additional fertilization, the Pothos might starve not only the algae but also other plants in the tank.

Are you tempted to add a Pothos plant to your aquarium? The process is straightforward.

As long as the plant has some root sprouts, you can submerge the roots and stems underwater, keeping the leaves out of the tank.

You don’t have to plant the roots in soil. But you should anchor the plant, so it doesn’t drift around.

How to Keep Phosphate Level Low in Aquarium?

Remember, there are two main sources of phosphates in the aquarium. Indirect sources are most common and include fish waste, uneaten food, and dead plant matter.

Direct sources include replacement water, aquarium salts, fertilizers, carbon filters, and pH buffers.

To keep phosphates low, you must focus on these causes individually. It seems overwhelming, but it’s quite simple once you’ve established a routine.

Here’s what to do to keep phosphates within an ideal range:

– Cut back on feeding

The easiest way to reduce phosphate concentrations is to eliminate the main source. And fish poop and uneaten food are the primary causes of breakdown products like phosphates.

Cutting down on the food amount and frequency helps you solve both problems simultaneously.

Check your fish species profile. Some fish may need to eat twice a day, while others need only one meal.

Also, adjust the food quantity to the number of fish in the tank. As a rule of thumb, the ideal food amount for fish is something they can consume within two minutes.

– Remove uneaten food right away

Stick around to observe your fish’s eating habits. Are your fish slowing down and no longer interested in the food?

That means they’re probably full. If that’s the case, grab your net and scoop out leftovers floating in the water.

You don’t want to let uneaten food in the tank. Fish flakes and pellets break down rapidly, releasing more phosphates and nitrates into the aquarium.

It’s best to take care of the leftovers before this happens.

– Don’t skip on tank maintenance

Even after cutting down on the food, there will still be some leftovers you’ve missed.

Fish waste and dead plant matter also accumulate in the aquarium, releasing toxic breakdown products.

So, remember to siphon the substrate and regularly wipe the tank glass and décor.

– Do more frequent water changes

You may not always feel like it; it happens to all of us. But putting off water changes will only make your job harder down the line.

If you’re like me and prefer to do one to two big water changes monthly, you know how murky the water can get.

Ideally, you should do smaller but more frequent water changes. This will keep your tank cleaner and minimize the risk of nitrate and phosphate buildup.

A small 15% weekly water change will work wonders if you keep this habit.

– Test your water source

Are you doing everything right, but the phosphate levels are still high? In the absence of debris or fish waste, the most probable source is the water itself.

Grab your testing kit and take a sample of your source water.

Tap water can have an average phosphate level of 1 mg/L, but it can also be higher, depending on your area.

Dechlorinating water treatments might make the water fish-safe, but it won’t take care of the phosphate concentrations.

If your water source is high in phosphates, you may want to try reverse osmosis water, distilled water, or deionized water.

– Check your filter media

Activated carbon media offers excellent chemical filtration to keep the water clear and odorless.

However, certain carbon media can also leak phosphate into the water. You need to research the products you buy carefully.

Ideally, you want a product that states it won’t leach phosphates into the tank.

You can also include phosphate-absorbing filter media alongside your activated carbon.

Carbon cartridges formulated for marine aquariums are also more stable and unlikely to leak phosphates.

Saltwater tanks, especially reef aquariums, need very low phosphate levels. This specially formulated chemical media provides that.

– Choose water treatments carefully

Water conditioners like pH and hardness buffers alter water chemistry by adding trace elements, including phosphates.

Avoid using such products unless necessary. If you need a water conditioner, read product labels carefully and choose the brand with the lowest phosphate concentration.


Phosphate is present in most freshwater tanks. The most common source is decaying matter, such as uneaten food, fish waste, and dead plant leaves. Small concentrations are safe for aquarium pets.

Phosphate is also crucial for plant growth and nutrient absorption.

However, when phosphate concentrations are too high, you’ll encounter issues with your tank.

High phosphates encourage algae blooms, reduce water oxygen levels, alter water pH and hardness, and may cause nutrient deficiencies in aquarium plants. Fortunately, getting the phosphate concentrations under control is quite easy.

For quick and effective removal, look no further than filter media such as Seachem PhosGuard, Fluval ClearMax, or ROWAphos.

These products are easy to use and help reduce phosphate levels in just a few days.

Of course, you should also remember aquarium maintenance and water changes to prevent recurring phosphate buildup.

Author Image Fabian
I’m Fabian, aquarium fish breeder and founder of this website. I’ve been keeping fish, since I was a kid. On this blog, I share a lot of information about the aquarium hobby and various fish species that I like. Please leave a comment if you have any question.
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