How To Get Rid of Protein Foam in an Aquarium

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by Jason Matthews


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Many things may cause the foam to form on the surface of your aquarium water. Some of these things are benign, while others indicate more serious problems. Protein foam is one cause of foamy aquarium water that you should deal with quickly.

Protein foam is not an emergency, but you should clean it up as soon as possible. The easiest way to get rid of protein foam is to clean your entire tank. Change the water, clean the tank and filter, clean any decorations, and trim the plants. 

Protein foam is normal. It is usually not a cause for alarm. Read on to learn about the causes of protein foam, and how to thoroughly clean your tank to get rid of protein foam in an aquarium. 

What Is Protein Foam?

Protein foam is a white biofilm that forms on the surface of the water in your aquarium tank. It usually forms in one location, and unlike other types of aquarium foam, it usually gives off an unpleasant smell.

Protein foam is the result of the buildup of organic waste such as food, fish waste, or dead creatures. This buildup forms a film on the surface of the water that traps oxygen just under the surface. Eventually, the oxygen forms small bubbles that stick together and create a smelly foam.

Protein foam is more likely to occur in saltwater aquariums, but it can occur in freshwater aquariums too. 

Causes of Protein Foam

Protein foam is usually caused by improper maintenance of your tank. Not cleaning the tank often enough, or not cleaning it well enough can leave behind food particles and fish waste that build up over time.

Another frequent cause of protein foam is dead and disintegrating fish carcasses. If a fish in your tank dies and you don’t notice, it will slowly rot and release protein into the water. Check for dead fish in your tank regularly and remove them when you find them.

Finally, decaying plants can also produce protein waste. Just like animals, plants are made of protein. When they decay, they release that protein into the water.

Why Is It Important To Clean Up Protein Foam?

While protein foam is not an immediate emergency, it’s a good idea to deal with it as soon as possible. Over time, protein foam can deplete the oxygen in your tank’s water and throw the delicate ecosystem of your tank out of balance.

When there is excess protein waste in your tank, good bacteria will begin working overtime to try and break it down. These bacteria require oxygen to break down (oxygenate) waste as part of the nitrogen cycle. As the bacteria reproduce to handle the excess load, they will sap more oxygen from your tank’s water. 

Low oxygen in a fish tank can become an emergency very quickly. Most aquarium fish will not survive longer than a day in a low-oxygen tank.

Related article: How to add or remove nitrates safely

How To Get Rid of Protein Foam In an Aquarium

The only way to get rid of protein foam in an aquarium is to clean the tank thoroughly. Take care when cleaning that tank that you don’t destroy the beneficial bacteria colonies. You should also check for decaying plants or fish carcasses. 

We’ve outlined the materials you will need and the cleaning process below.


To perform a proper cleaning of your fish tank, you will need the following:

  • Gloves
  • Scraper and razorblade (plastic if you have an acrylic tank)
  • Gravel vacuum
  • Bleach
  • Bucket (brand new or only used for this tank)
  • Aquarium lime remover
  • Filter media and brush
  • De-chlorinator

Check for dead fish or other animals

If there are any dead fish in the tank, remove them immediately. Make sure to check underneath all rocks and decorations and inside plant cover. 

Do a 40% water change

Depending on how bad the protein foam is, you may or may not need to change the water. If the foam is really bad, we recommend a 40% water change. 

Don’t attempt to change all the water at once. You will destroy the beneficial bacteria in your tank and throw off the balance of the ecosystem.

Related: How to clean sand in your aquarium

Scrape the side of the tank

Scrape down the sides of the tank with a scraper to remove algae and other buildups. If the algae are particularly stubborn, you may need to use a razor blade to remove them. 

Buy your scrapers or algae pads from a pet store, not from a home department store. Pads from a regular store might contain chemicals that are harmful to your fish.

Clean decorations and rocks

Remove all decorations, or at least decorations with noticeable algae growth. Do not wash them with soap. Soap is difficult to remove and even a trace of soap residue can be harmful to fish. 

If they don’t come clean with a good scrub in warm water, soak rocks and decorations in a 10% bleach solution for 15 minutes.

After soaking, rinse them thoroughly until all traces of any chlorine smell are gone. You can also rinse them with a de-chlorinator to remove chlorine. Do not put them back in the tank with chlorine on them.

Clean and trim plants

Look for any plants with dead or decaying leaves. Trim or remove any dead plant matter.

Some live plants can be treated with bleach to remove algae. Stem plants cannot be bleached. 

To bleach plants, use a 5% bleach solution and soak for 2-3 minutes. Rinse well to remove every trace of bleach.

Set aside the plants, rocks, and decorations in a bucket while you vacuum the gravel.

Vacuum gravel

Use a water siphon to clean the gravel. The siphon should stir up the gravel and suck up debris without also sucking up the gravel. Leave the plants and decorations outside the tank during this step so that debris doesn’t settle on them.

Clean the filter two weeks later

Once your tank is nice and clean, let it sit for two weeks before cleaning the filter. Cleaning the tank will have depleted the bacteria colonies in the tank. Fortunately, there should be plenty of bacteria in the filter.

If you clean the tank and filter at the same time, you might destroy too much good bacteria. When there is not enough bacteria in the tank to break down fish waste, it can cause a dangerous ammonia spike.

Replace the filter media and clean the filter tubing and other components with a small brush.

Ongoing Maintenance

Once the tank is clean, check for dead fish and decaying plant matter regularly, and be sure to perform regular water changes and cleanings to keep protein foam from building up again.


Jason Matthews

My name is Jason Matthews, and welcome to my website. When other kids were bragging about how their dog could sit and roll over, I was bragging about my latest Betta Fish and the cool sea castle I just added to his aquarium. 

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