Why are there bubbles in my fish tank? (6 Explanations)

Why are there bubbles in my aquarium header

Some time ago, after taking a look at my beloved aquarium, I was very worried because I witnessed an unusual sight.

I noticed foam on its surface and couldn’t tell why there were tiny bubbles in my aquarium.

I wondered if they could be an indication of something bad going on in the water column and if it could harm my aquatic animals.

The small air bubbles sometimes appeared on the aquarium glass after a water change, but they usually dissipated in a short time.

This time they stayed on top forming a kind of shiny foam which I later discovered was a protein film. Fortunately, I did some research and found out what causes microbubbles to appear in aquariums and how to get rid of them.

In this article, I will share my knowledge and experience to help you.

Why are there bubbles in my aquarium?

In fact, in aquariums, bubbles form for many reasons and most of them are not of concern.

A few common but benign ones are:

  • Bubbles often appeared on the surface of the aquarium due to the agitation created by your airstone or HOB filter. In this scenario, they will spawn quickly after reaching the top;
  • Air bubbles would also form on your tank glass after a water change which is natural. This happens if you added low temperature water. This effect is due to the ability of cold water to retain more oxygen. As the water temperature rises, oxygen is released which creates tiny bubbles in your aquarium.

There are even more reasons why you can witness this aquarium phenomenon without it being a sign that something is wrong.

I will explain them in detail below.

That being said, in some cases bubbles can form foam in your aquarium.

It may indicate that you need to take a closer look at the water quality.

Here is the reason behind the bubbles that appear in your aquarium when they can signal a bad thing:

If there are foamy bubbles covering the surface of your aquarium and not popping, they are likely caused by organic waste in the water column. Proteins from decaying fish droppings, uneaten food, and other decaying organic matter attach to tiny air bubbles and create a protein film around them.

In the following sections, I will go over in detail:

  • the different causes of bubbles appearing in aquariums;
  • what they indicate;
  • How to get rid of them.

1. Organic waste in the water column

surface microbubbles

by sydney

Decomposing organic matter in an aquarium is usually the by-product of:

  • fish waste;
  • food scraps;
  • dead plants;
  • other debris.

This material often attaches to the surface of air bubbles in your aquarium water, creating a stable film that traps oxygen. This occurrence is more prevalent in saltwater aquariums, but can also appear in freshwater aquariums.

You can get rid of the bubble cover by increasing the agitation of the water surface.

This essentially makes the water move more.

If you have a saltwater aquarium, you can also use a dedicated protein skimmer to remove proteins and oils from the water column.

However, if the protein film still covers the top of your aquarium, you should use your water test kit to measure ammonia and nitrite levels.

If the microbubbles do not dissipate and foam covers the surface of the water, it may be a sign that there are not enough beneficial bacteria to deal with the accumulated organic waste.

If your water test shows that the ammonia and nitrite readings are above 0 ppm (parts per million), you should take steps to reduce them.

To do this, you can perform partial water changes.

Changing the water can bring toxic ammonia in an aquarium back to desired levels and help get rid of microbubbles permanently. The same method can be used to reduce nitrite levels, but if that doesn’t help, visit the links to learn more about other ways to do it.

Author’s note: Protein moss often forms in new aquariums where the nitrogen cycle is not complete. This is also usually the case in tiny aquariums, as waste can accumulate much faster in smaller aquariums.

2. Release of saturated oxygen after water change

water change bubbles

by Necessary-Shift-9029

Sometimes you may see tiny air bubbles on the decor or glass walls of your aquarium after a water change.

This is likely due to the temperature equalizing between the new water and the aquarium water.

The fact is that colder water can trap more oxygen than warm water.

Once the temperature of the new water rises after adding it to the aquarium, oxygen is released, creating microbubbles.

Most of the time, you shouldn’t worry about it, because it’s completely natural.

It is not recommended to pour cold water into your aquarium, but the small bubbles themselves will disappear in a short time.

To make them pop faster, you can increase the agitation, which will push them to the top of the tank and cause them to dissipate.

Author’s note: In some cases, the rapid release of gas could be dangerous for your aquatic animals. This happens if you perform a larger water change without taking precautions.

The more intense gas release could cause bubbles to form in your fish’s eyes, blood and fins. This is known as Gas Bubble Trauma, which is sometimes the reason fish die or become stressed after a water change.

Therefore, I recommend always checking that everything is in order if you change more than 30% of the aquarium water.

Another way to protect your fish from potentially harmful bubbles is to stir the water before adding it to their tank.

Agitation will increase gas exchange and avoid bad consequences.

3. Chemical contamination from detergents

Chemicals from cleaning detergents can accidentally end up in aquarium water.

The result is frothy bubbles on top of the tank.

These substances could be dangerous for your fish, invertebrates and plants.

One scenario is that your tank doesn’t have a lid and you’re using spray disinfectants or detergents nearby.

Some products can penetrate the aquarium water and create a shiny layer of foam with a rainbow hue. The same can happen if during regular aquarium maintenance you use cleaning tools that have already been used for other cleaning purposes.

If you doubt that cleaning detergents are causing small bubbles to form in your aquarium, you should immediately perform a water change.

4. Male betta fish making a bubble nest

betta female bubble nest

by kayfeldspar

Some species of fish, such as bettas and gouramis, build bubble nests as part of their breeding ritual. The fish blows tiny air bubbles covered with a special saliva which then form a mat on the surface of the water and do not burst easily.

This behavior is completely natural and means your pet fish is ready to mate.

Male bettas typically built their nests around or under plant leaves near the top of the tank. Indeed, tall or floating plants give Betta fish a sense of security.

Even though bubble nests are made by male specimens, you can also see tiny bubbles in tanks with female betta fish. This is because all Siamese fighting fish have what are called “maze” lungs.

This type of lung allows them to breathe oxygen directly from the surface of the aquarium.

The puff of air the Betta takes in at the top of the tank can cause small bubbles of oxygen to form, which is not a bad thing.

5. Plant Beading

plant beading

by ambo_j

If you keep aquatic plants in your aquarium, you may notice white bubbles forming on the surface of their leaves.

This is an all natural process, known as vegetable beading.

It is the result of photosynthesis and is due to the release of oxygen. Since the water in the tank is not able to hold all the oxygen produced there, tiny bubbles would start to appear on your plants and float on the surface of the water.

It is not a cause for concern and will not harm your aquatic inhabitants.

On the contrary, it indicates that your plants are thriving and there is plenty of saturated oxygen around them.

6. Water agitation

Microbubbles are often formed by too much agitation of the water and sometimes to the point that the water appears cloudy. Agitation following cleaning or other aquarium maintenance is one scenario.

On the other hand, the bubbles can also appear near a powerful cartridge filter or following a working air stone. In these cases, a newly formed bubble would rise to the top of the tank and quickly dissipate into the air.

That being said, setting your air pump or aquarium filter to operate at maximum capacity can create too much unnecessary water agitation. Although aeration is beneficial for an aquarium, it does not need too much.

Also, some aquatic animals can get a little stressed if there is too much movement in the water column.

Conversely, insufficient movement in the water can lead to stagnant areas on the sides of the aquarium where the tiny bubbles could get “stuck”.

In other words, when it comes to adjusting your filters and aeration units, moderation is key.

Last words

You can’t expect an aquarium not to have a few bubbles here and there, but too much of anything can become a problem.

I hope you found my article useful and got the answers you were looking for.

If any other questions arise, feel free to leave them as a comment in the section below.

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