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How to Remove Phosphates From Aquariums? 2 Recommendations

Lindsey Stanton Profile Picture

By Lindsey Stanton

Aquarium cleaning fish tank

There is no doubt that aquariums are cool things to have in your home. Fish are awesome pets to have no doubt, but they do come with their problems. One of these problems is that you have to deal with aquarium water and all of the organic processes that affect aquariums water.

Here, we are talking about the unwanted addition and creation of phosphates in aquarium water. We also want to talk about their effects, how to prevent them from building up, and how to treat aquarium water when there is too much phosphate present.

Today, we want to focus on how to remove phosphates from aquarium water, but first, it’s important to understand the effects and desired levels of phosphates.

aquarium plant dividerWhat Are Phosphates?

Phosphorus is an organic compound that is present in all organic matter, which includes fish, plants, and even fish food too. Phosphorus is very important for the body of fish and of people. It is used in the building of cell membranes, for bio-chemical processes, and as a source of energy too.

Phosphates are a byproduct of the rotting or decaying of animals, plants, and other organic matter too. When these things decay, phosphorus turns into phosphates, and it can be very dangerous for the plants and fish in your aquarium.

When fish food, plants, and other things decay, they cause phosphates to leach into the water, gathering on plants, in the substrate, and in the filter too.

A high concentration of phosphates in aquarium water has many negative effects on all aquarium inhabitants, so you must stop the buildup from happening before it occurs and quickly takes care of any phosphate problems as they occur. You want to be preventative here, but also reactive if necessary.

fish tank with filter hose
Image Credit: RaKav007, Shutterstock

Effects of Phosphate in Aquarium Water

What is at least fortunate about phosphates in your aquarium water is that they do not directly harm fish. This stuff can be present in really high amounts and still not be a direct threat to your fish. However, what is a threat is the fact that phosphates in high amounts, and even in relatively small amounts, it can cause some big algae blooms to occur.

Not only are these algae blooms unsightly and a pain to clean up, but too many algae can cause oxygen levels in aquarium water to nosedive. Low dissolved oxygen levels in the water are a threat to your fish.

Your fish need to breathe oxygen, so if there is not enough of it in the water, your fish won’t be able to breathe. Therefore, it is pretty important to control phosphate and remove it from the fish tank as much as possible.

Desired Phosphate Levels in Aquarium Water

When it comes to the desired amount of phosphates present in aquarium water, the level should be no higher than 1.0 parts per million at most. Even that is already a favorable amount for algae growth.

Anything above that can easily cause algae blooms to occur. If the phosphate levels in the water reach 3.0 parts per million, you are pretty much guaranteed to suffer from a pretty severe algae outbreak.

You should get yourself a phosphate testing kit. They are easy to find at any pet or aquarium store. Keep in mind that these kits only test for organic phosphates, not inorganic phosphates, so you will technically only be measuring a portion of this substance in the water.

Dissolved organic phosphate levels should be kept to a minimum, with 0.5 parts per million being the level you should aim for.

Sources of Phosphate in Aquariums

There are a few different sources of phosphates in aquariums, some of which are easier to deal with than others. So, what are the sources of phosphates in your aquarium? Where is this stuff coming from?

  • As we said, decaying organic matter is a prime contributor of phosphate in fish tanks. Therefore, one of the biggest sources is uneaten fish food. If you don’t clean this stuff out regularly, it releases phosphates into the water.
  • On that same note, fish waste is also a contributing factor to increased phosphate levels. The fish waste still contains a lot of organic matter, even undigested food, that can release phosphates into the water as it breaks down.
  • Another thing that can add phosphate to the aquarium water is plants that are decaying. All matters of decaying organic matter have this phosphate-creating effect.
  • If you have any dead fish or plants in the tank, the decay of those things will also cause a buildup of phosphates in aquarium water.
  • One of the largest sources of phosphates in aquarium water is the tap water you use to fill up your fish tank. Tap water often contains a lot of dissolved organic matter, and therefore contains phosphates too.
  • Carbon does release phosphates into the water. If you have an activated carbon filter, it could very well be releasing phosphates into the water. However, modern carbon chemical filtration units should be specially designed to prevent the release of phosphates into the water.

Also, there are various additives and pH buffers that are added to aquarium water which also contain phosphates or create phosphates.

In short, the sources of phosphate in the aquarium water include the following:

  • Plant decay
  • Fish decay
  • Fish waste
  • Uneaten food
  • Carbon filter media
  • Can already be in the water
  • DH buffers
  • pH buffers
  • kH buffers
  • Aquarium salts
  • Dying and decaying algae
fish tank
Image Credit: S-F, Shutterstock

How to Remove Phosphates From Aquarium Water

Dissolved organic phosphate does build up fairly easily, but thankfully, it is not all that hard to remove. It tends to settle in the bottom of the tank and on decorations, plants, and rocks.

It may sound like a pain in the butt, but the fact that phosphate is dissolved in the water and tends to settle on objects is somewhat of an advantage when it comes to removing it. How to remove phosphates from aquarium water is what you are about to find out right now.

Water Changes

One of the fastest ways to get rid of phosphates in aquarium water is to do a partial water change. You can do a 25% or even a 30% water change per week if there is way too much-dissolved phosphate in the water.

Just remember that due to water chemistry changes you can’t change all of the water in the tank at once.

A man with hose and bucket, changing the water in a well planted, large aquarium
Image Credit: hedgehog94, Shutterstock

Tank Cleaning

You will want to take an algae scrubber and tank glass cleaner to remove as much residue from the interior tank walls as possible. Like we said before, this stuff tends to cling onto surfaces, so cleaning the large walls of your aquarium should help quite a bit. At the same time, you should also use an aquarium vacuum to suck up as much phosphate-releasing debris as you can.

Cleaning Plants & Decorations

You also need to clean various rocks, pieces of driftwood, plants, and other decorations too. Using a mild bleach solution to clean them is a good idea.

Soak the plants and rocks in a 10% bleach solution, then soak them in water for 10 minutes, scrub everything off, rinse it off, and place everything back into the tank.

Credit: Igor Chus, Shutterstock

Using a Phosphate Absorber

There are special phosphate-absorbing liquids that you can use to get rid of phosphate in the water. These can be a little pricey, but they are specially designed just for this task.

Be sure to follow the directions on the bottle closely because using too much of this stuff can have other negative effects.

Protein Skimmer

A protein skimmer is a great way to remove phosphates from the water, plus a great way to remove debris that is releasing phosphate. Just keep in mind that protein skimmers only work for saltwater tanks and not for freshwater tanks.

AQUATICLIFE 115 Mini Internal Protein Skimmer:Filter

Fix the Underlying Issues

We have discussed all of the causes of elevated phosphate levels in aquarium water above. You need to fix these underlying issues to stop buildups from occurring, plus to make the above methods of phosphate ridding effective.

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How to Prevent Phosphate Buildups in the Fish Tank

Yes, you can remove phosphates from the water once they are therethe majority of them anyway. However, the best way to deal with this issue is to be preventative, not reactive.

So, the best way to start is to prevent the build-ups from occurring in the first place. How do you prevent phosphate buildups?

  • Flake and pellet food is a massive contributing factor to elevated phosphate levels. Therefore, make sure that you do not overfeed your fish. Uneaten flake food releases a whole lot of phosphates as it dissolves. You should aim to find a flake food that is free of phosphates as it will help a lot. If you do use phosphate-containing food, use it sparingly.
  • Overfeeding your fish also causes them to produce more waste, which in turn causes elevated phosphate levels. Making sure to not overfeed your fish is a great way to help combat this problem.
  • Remove all kinds of things from the water that could be contributing to elevated phosphate levels. This includes uneaten fish food, fish waste, dead and decaying fish, as well as dying and decaying plant matter.
  • Keep engaging in regular water changes and cleaning. Yes, water changes and tank cleaning are great ways to get rid of elevated phosphate levels, but they work even better when used as preventative measures. This includes 10% weekly water changes, cleaning tank walls, vacuuming substrate, and cleaning plants, rocks, and decorations.
  • Make sure that you have a filter that is up to the task. First and foremost, make sure that the filter is always clean and free of debris. Debris can cause inefficient filter function, plus it can release phosphates into the water too. Moreover, make sure that if you are using carbon in your filter, that it has been specially treated to prevent the release of phosphates into the water.
  • Don’t use water treatments unless necessary. pH and DH treatment chemicals can cause elevated pH levels. If you have to use any of these kinds of products, do a lot of research and make sure to choose the ones with the least possible amount of phosphates in them.
large fish tank with plants and filter
Image credit: M-Production, Shutterstock

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The 2 Best Phosphate Removers for Freshwater Aquariums

In terms of products, we would recommend using the below 2 aquarium phosphate removers.

1. D-D Rowahos Phosphate Remover

D-D Rowahos Phosphate Remover

Here we have a great phosphate remover, one that can be used simply as filter media. All you have to do is insert it into your fish tank filter where the rest of the media goes.

You can choose to place it in a media bag and just put it right in your filter, but the better way to go is by inserting this phosphate remover into a media reactor. Yes, it will cost you a bit extra, but will also work a lot more efficiently.

This stuff is proven to effectively remove phosphate from the water, and it will not leach the phosphate back into the water. This option can be used for freshwater and saltwater aquariums.

  • Large quantity
  • Simple to use
  • Very effective
  • Do not leach phosphate back into the water
  • For salt and freshwater tanks
  • Requires a media reactor for best efficiency

2. Fluval Clearmax Phosphate Remover Filters

Fluval Clarmax Phosphate remover

This is another great option to go with. What is convenient about this phosphate remover is that already comes complete inside media bags.

These media bags can be placed right into a filtration unit or even directly into a fish tank as well. They are proven to effectively absorb phosphates without leaching them back into the water.

This product can be used for freshwater and saltwater aquariums. Keep in mind that each little filter can treat a tank of up to 27 gallons.

  • Can be put in a filter or right in the tank
  • Comes in media bags
  • Super easy to use
  • Absorbs without leaching
  • For saltwater and freshwater tanks
  • One filter only treats 27 gallons

wave tropical dividerFAQs

Will carbon remove phosphates?

Yes, carbon will help to remove aquarium phosphate from your aquarium. Activated carbon does not directly remove phosphates from the water, but it does break down organic compounds, thus slowly breaking phosphate down into other components.

Moreover, some activated carbon filters will remove phosphate from the water, but these activated carbon filters are also known for leaching phosphate back into the water.

Can high phosphates kill fish?

Generally speaking, no, high phosphate levels will not directly kill your fish, but it can lead to other issues.

For instance, high phosphate in aquariums can cause algae to bloom in great numbers, which then decreases the level of dissolved oxygen in your aquarium.

Eventually, this may lead to your fish suffocating.

Can phosphates kill corals?

Yes, high levels of phosphates can kill your corals. For one, there is once again the issue of high phosphate levels causing algae blooms, which then leads to decreased oxygen levels. However, phosphate is very bad for corals and can kill them very quickly.

For this reason, most people with a saltwater reef tank use a protein skimmer or a media reactor with phosphate remover to take care of this issue.

Does GFO remove phosphates?

Yes, this is exactly what GFO is made for. GFO stands for Granular Ferric Oxide, a reddish-brown powder that comes in the form of compacted granules. The main purpose of this GFO is to remove phosphates from the water, thus inhibiting algae growth and protecting your corals.

aquarium plant dividerConclusion

Elevated phosphate levels may not be your number one concern because they are not a direct threat to your fish. However, the resulting algae blooms and oxygen depletion in the tank can very well be dangerous, or just annoying at the least. So, as you can see, there are many ways to prevent phosphate buildups, plus some good ways to deal with this situation once it occurs.

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Feature Image Credit: Open Mind Art, Shutterstock

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