Why Does My Fish Tank Have Bubbles on the Glass?

Ever noticed tiny air bubbles clinging to the walls of an aquarium?

Then you’ve probably wondered what these bubbles are made of and what their occurrence indicates?

Today, in this guide, we will discuss all your concerns regarding the occurrence of bubbles in the fish tank.

The bubbles forming in the tank are usually not due to any serious problems and occur due to natural reasons.

We will look at each possible reason why your aquarium’s wall is covered with tiny air bubbles.

Reason #1 – Oxygen Saturation of the Water is Raised

Plants in the fish tank are a great source of oxygen. It is more common to see air bubbles appear on plants in the tank than on the glass.

This phenomenon is that plants are producing more oxygen than needed in the tank.

However, more oxygen in the tank water is not always a bad thing. Your fish require a certain amount of oxygen in the tank to survive.

Hence, it must worry you if you stop noticing the air bubbles on the plants for a while.

The appearance of air bubbles on the plant may look like tiny beads or pearls, so this phenomenon is called pearling.

In case of excessive pearling, a quick oxygen drop or an air pump can help bring the oxygen levels back to normal again.

Reason #2 – Aeration Malfunction

If you start noticing that the fish in your Aquarium swim up to the surface more often than usual, an aeration malfunction must be suspected.

We have already established that fish need a certain amount of oxygen in the tank to survive.

If oxygen levels in the water go below the optimum level, the fish in the tank will start to exhibit peculiar behavior.

Most fish will find it their responsibility to fix the oxygen saturation. Such fish will swim to the water’s surface and swallow some air.

Fish swallow the air to produce air bubbles in the tank. They end up overcompensating for the lack of oxygen in the tank.

Hence, excess oxygen gets deposited onto the walls of the tank or plants.

Reason #3 – Formation of Air Pockets

Air pockets are formed when small amounts of air get trapped under some object in the Aquarium.

Such things usually include plants and decorations. At times, the air gets trapped under the substrate as well.

Now one may wonder how the air gets trapped in the first place and how do you detect it?

The air usually gets trapped while pouring water into the fish tank. Hence, the more water you pour in, the more air pockets form.

Trapped air pockets then try to leak from their source by creating tiny air bubbles on the tank wall.

Such air bubbles appear in evenly spaced outlines on the tank wall.

Thus, the appearance of air bubbles in the form of beads on a string should indicate that air pockets were formed in the tank while adding water to it.

As more water is added to the tank, the number of lines of air bubbles increases on the tank wall.

Reason #4 – Filter Outlet is Placed Incorrectly

Another very common reason why there are air bubbles on the walls of your fish tank is that the filter is not placed correctly.

The filter outlet blows out the air in the tank. If the outlet is placed well above the water’s surface in the tank, a stream of water will form in the tank.

The stream of water carries air bubbles. These air bubbles eventually cling onto plants and decorations in the tank.

If the stream directly hits a wall of the tank, then many air bubbles will appear on the walls of the tank.

The correct way of placing the filter in the tank would be to ensure that the filter outlet is almost at the same level as the water surface.

You can even submerge the filter outlet just a few millimeters below the water surface.

Placing the flitter outlet in such a way would guarantee that all air bubbles escape through the water surface and none remain in the water to cling onto the tank’s walls.

Reason #5 – Use of Fish Tank Heater

Installing a heater in the fish tank can result in unwanted air bubbles in the tank.

This happens because cold air can hold more dissolved oxygen than warm air of the same quantity.

This entails that warm water has a lesser saturation point for oxygen than cold water.

Hence, when the heater is turned on, and the water warms up, it loses some of its oxygen in air bubbles.

Warm water cannot hold the same amount of oxygen as cold water.

However, such a rise in temperature causing air bubbles to form on the tank walls should not require you to do anything to fix it.

As the water temperature returns to its original temperature, the tiny bubbles on the walls would disappear automatically.

Reason #6 – Presence of Dead Algae in the Fish Tank

Treating your tank with algae has a lot of benefits for the fish, but if the algae start dying, it must be replaced immediately.

Accumulation of dead algae in the tank causes decomposing products like ammonia to build up in the tank.

The ammonia gas will be observed as tiny bubbles forming in the tank. The bubbles will appear transparent like any other air bubbles formed in the tank due to natural causes.

Once these ammonia bubbles appear in the tank, it won’t just be enough to remove the dead algae.

You will have to replace the tank water as well. It would also be beneficial to get a water conditioner as it would help a lot in the long-term maintenance of the tank water.

Also read: How to Get Rid of Black Algae in a Fish Tank?

Reason #7 – Presence of Bubble Nests Forming Fish

Certain species of fish like catfish and betta fish are bubble nests former.

Such fish are required to firm the bubble nests in their natural habitat. Hence, their instinct is to do the same in the fish tank.

The purpose of the bubble nest is to contain fish eggs.

It is a natural thing for such fish to form bubble nests. These bubble nests will cause no harm to the tank’s environment.

Such bubble nests only indicate that your fish are healthy and are acclimatizing well.

Hence, it is best to leave the bubble nests untouched till you are due for your next tank clean-up.

Is the Presence of Air Bubbles a Sign of Any Harmful Condition in the Tank?

We have discussed almost all the reasons behind the presence of air bubbles in the tank. The air bubbles seem to hinder the clear view of the tank.

Other than this minor inconvenience, there is no reason you should be worried about the presence of these bubbles.

It must be noted that the presence of bubbles in the tank mainly indicates that your fish are healthy.

Bubbles are naturally formed in the water bodies like lakes and rivers. Hence, it further reiterates that bubbles in the tank only make the tank’s environment as close to the fish’s natural habitat.

This explains why most aquariums have air stones installed to create air bubbles in the tank.

However, the formation of excessive bubbles that may take the form of foam must be addressed immediately.

It could indicate that water conditions are no longer fit for your fish to live in—foam forms due to excess protein in the water.

Protein coats the bubbles and prevents them from escaping the water.

How to Remove Bubbles Stuck on the Walls of the Fish Tank?

The process of removing bubbles stuck on the walls of the tank depends on the source of the bubbles.

If the bubbles are coming from the air pockets formed while filling the tank, there isn’t much you need to do. Such bubbles would disappear on their own.

Most bubbles formed in the tank are lighter dense than water. Over time, such bubbles would naturally rise to the surface and escape the tank.

Hence, all you need to do is wait, and your tank walls clear themselves.

In addition to this, if your tank has a well-installed aeration system, it will naturally speed up the removal of the bubbles.

However, if you cannot wait to get off the bubbles on the walls of your tank- you can take matters into your own hands.

And literally, you will need to use your hands to clear the tank walls.

An algae scrubber can also be used. Just wipe your tank with your hand or the algae scrubber in a U-shaped movement.

It will feel like you are trying to scoop out the bubbles.

The Bottom Line

We hope that we have answered most of your queries regarding the mysterious appearance of bubbles on the tank walls.

It should give you some relief that most of these causes do not cause any harm to your fish and can be removed by simply waiting it out.

Stay tuned for more valuable guides and stories.

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