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Bubbles & Foam in Your Fish Tank

Friend or Foam – Bubbles & Foam in Your Fish Tank

Updated on February 03, 2023
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Reviewed by Petco’s Animal Care
Education and Compliance (ACE) Team

Protein | Cleaning Products | Natural Causes | Pearling | Fish Medications | Bubblenest Foam | Recommended Products for Aquarium Foam or Bubbles    

bubbles on plants in fish tank

It is not uncommon to occasionally observe oil, bubbles or foam forming in your aquarium. Before reacting, you need to determine if it is natural or dangerous. We going to review some common causes and when you should be concerned.

Why are there bubbles in my fish tank?

Underwater environments depend on gasses like oxygen and CO₂, so your aquarium is naturally prone to bubbles and foam. Your aquatic life and equipment naturally produce bubbles that benefit your tank, but bubbles and foam can also signify poor water quality. Knowing the difference is vital to aquarists, so let’s discuss how to identify good and bad bubbles and foam.

Why are there bubbles at the top of my fish tank?

If you recently cleaned your aquarium or performed a water change, you may see bubbles resulting from your aquarium heater increasing the water temperature. However, if the bubbles have a rainbow shimmer, it’s likely you didn’t properly rinse your tank or decor cleaning solution, which could harm aquatic life. Bubbles can also be caused by any medication you recently added.

Why is there foam in my fish tank?

The most common cause of foam is an excess of waste from your pet’s poop, uneaten food or decaying plant matter. The decomposing material breaks down to proteins and attaches to bubbles to form foam but can be easily removed with protein skimmers. If the foam has unnatural coloring, it may indicate a manmade chemical harmful to aquatic life.

Protein

There are foams and oils that form in an aquarium which are caused by proteins. Protein foam or oily biofilms are created when waste proteins, fish waste, decaying debris, deceased aquatic life, or natural oils from food attach to small air bubbles. Saltwater aquarists can use a protein skimmer to extract proteins and oils from the water column. Unfortunately, protein skimmers do not work as effectively in freshwater due to the inability of freshwater to create the small air bubbles needed. These foams or oils are not initially deadly, but they are a sign that your aquarium needs to be cleaned and a water change is in order to help reduce this buildup. Increased surface agitation will also assist with breaking up these oils and increase gas exchange.

Cleaning Products

Concerning bubbles or films could be caused by something that has a high potential to cause harm to your aquatic life. If the bubbles or the film on the water’s surface have a rainbow tint, they could be caused by cleaning products. These products can make their way into the aquarium through items that were used for cleaning and now used for aquarium maintenance. Aerosol based cleaning products can also enter the aquarium if used near an open top tank. If these rainbow-colored films or bubbles are discovered, aquatic life should be removed, the aquarium drained and all décor, heater and filtration rinsed vigorously to remove all contaminants. Any filter media should be discarded and replaced. 

Natural Causes of Bubbles in Your Aquarium

Foam and bubbles can also be created through agitation. One of the most common forms of bubble and foam production comes when setting up a new aquarium or performing your routine tank cleaning. When filling a new aquarium, a lot of agitation is created causing bubbles or a slight foam to form at the water’s surface. Filtration and aeration components can also create agitation at the water’s surface causing bubbles to form, but nothing to be alarmed about as these are completely natural.

You may notice bubbles forming on the aquarium glass, heater, and décor after completing a water change and asked yourself why? These bubbles formations have to do with water temperature. The incoming water, especially in the winter, is much colder than your tropical aquarium. Cold water can hold more oxygen than warmer water, so when this cold water enters the aquarium and mixes with the warm water, oxygen is released forming those little bubbles you are seeing. These are another form of bubbles in the aquarium you do not need to be concerned about.

Pearling

bubbles on plants

Does your aquarium have live plants?  You may notice little bubbles forming on your plants, often referred to as pearling. Pearling, which is desired by plant hobbyists, is a part of the photosynthesis process of absorbing carbon dioxide and releasing carbon dioxide, indicating that your plants are thriving. Just a reminder, algae is a plant that utilizes photosynthesis so it will create these little bubbles as well.

Fish Medications

Do you have any aquatic life feeling a little under the weather? Adding medications to your aquarium can cause a slight water thickening. Due to this viscosity change, those bubbles that would rise and pop quickly will take a little longer to pop.

Bubblenest Foam

betta creating a bubblenest

Bubble nesting fish can also be the cause of bubbles in your aquarium. Male Labyrinth fish species, like Gourami’s, Paradise fish, and Bettas build these bubble nests for their eggs to develop in.

Recommended Products for Aquarium Foam or Bubbles

Protein Skimmers for Saltwater Tanks

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