Why Are There Bubbles In My Fish Tank – 9 Reasons Why (and 7 Ways To Prevent it)

We all want clear glass and clear water in our fish tanks. However, sometimes we have bubbles messing up our view, and then we wonder – “why are there bubbles in my fish tank.” There are various reasons why (we will cover the top 9), and there are several ways to prevent bubbles (we’ll go over 7). Want to learn more? Read on!

Key Takeaways

  • Bubbles in your fish tank can be good, bad, or somewhere in between.
  • These bubbles can be the result of many factors, such as the aquarium filter, water quality, or labyrinth fish.
  • The best way to stop little bubbles from forming in your aquarium is by finding the thing that’s causing them.

What Causes Air Bubbles In Your Tank?

H2O, also known as water. The science behind our aquariums.

In order to make the water for our fish tanks, hydrogen needs to bond with oxygen. This means that there is always oxygen available in your aquarium in the form of H2O! But sometimes oxygen can start to appear in the form of annoying microbubbles that stick to the sides of the aquarium and decorations and might even create a mat at the surface of the water.

While they might look out of place, microbubbles are usually temporary in both freshwater and saltwater aquariums. In most cases, air bubbles will only stick around for a few days. But what causes these bubbles, and are they harmful to fish and invertebrates?

1. New Fish Aquarium

The most common time to see air bubbles form in the aquarium is in the few days following a new tank setup. Small bubbles clinging to the side of the aquarium and the surface of the water often leads new hobbyists asking “why are there bubbles in my fish tank”? It’s a good question!

Bubbles in a new tank are nothing to worry about and should be expected. This is perfectly normal and is the result of oxygen escaping from the substrate, decorations, and surfaces of the aquarium. They should dissipate within a week.

2. Air Stones And Filtration

The next obvious source of air bubbles in your aquarium is direct oxygen inputs, like an air pump or your filtration system. This equipment pumps oxygen into your tank in an attempt to create surface water agitation, which facilitates the gas exchange of oxygen and carbon dioxide between the aquarium and the atmosphere.

Both air stones and filters are great ways to introduce dissolved oxygen into the aquarium. The bubbles produced should be clear in color and pop almost immediately. Some bubbles created by the air pump may not pop right away and create an area of tiny bubbles on the surface of the water. This is usually nothing to worry about.

3. Water Changes

Water changes can also cause microbubbles. This can result from tank water agitation causing more oxygen to enter the tank, but it can also be due to differences in water temperature.

Cold water holds more oxygen than warm water. If new aquarium water is cooler than that already in the tank, this oxygen may be released through tiny bubbles that stick to the aquarium glass. This is not ideal if there are fish and invertebrates present in the tank due to stressful changes in water temperature.

Water change water should be the same water temperature as the existing aquarium water to prevent fish from going into shock. A several-degree difference can lead to tiny bubbles forming while also stressing out fish.

To help prevent this, new water should be heated with an aquarium heater to the desired temperature.

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4. Medications

Another reason why tiny air bubbles might form on the water’s surface is due to medication use. Many medications, like Hikari’s PraziPro1

Thus, any bubbles that form in the aquarium during this time are thicker than usual, leading to longer-lasting bubbles. This effect can be decreased by increasing water agitation, which is normally recommended when using strong medications. The bubbles formed should be clear, though some medications can cause an unusual shimmer or foam bubbles.

5. Oily Surface Layer

Look down at your aquarium. Do you see a rainbow or off-white swirls? This could be a sign that a contaminant is in your fish tank. Don’t worry just yet, though.

This contaminant can be organic or inorganic. The natural oil from fish food as well as from hobbyists’ arms and hands, can leak into the aquarium over time. Other organic waste and proteins can also build up and create an oily surface layer. In addition to the discoloration, this layer of oil and protein foam will prevent bubbles from rising all the way to the top of the aquarium.

Some hobbyists use paper towels to remove this layer periodically, but this is a temporary fix. The best way to prevent this is by improving surface movement. Hands and arms should also be thoroughly washed before performing fish tank maintenance.

The real problem happens if this sheen isn’t from a natural source and is the result of soap residue or contamination from other cleaning tools and products. Not only will this result in foamy bubbles on the water’s surface, but will also affect your fish’s ability to breathe, which can quickly prove to be deadly.

Keep cleaning products far away from the tank (including out of the air) and never use soap to clean an aquarium!

6. Poor Water Quality

Bubbles forming in the aquarium can be a sign of poor water quality, specifically concerning ammonia. Ammonia is a toxic compound that can burn fish’s gills and cause them to suffocate. Excess ammonia greater than 5 ppm can also cause the nitrogen cycle to stall in the aquarium, preventing beneficial bacteria from detoxifying the compound.

If bubbles seemingly appear out of nowhere in your fish tank, check for improper water conditions with a reliable water test kit.

7. Fish Nest

Not all foamy bubbles are bad, though. In fact, creating a bubble nest is the main way labyrinth fish species reproduce. This is most commonly seen with male betta fish (Betta splendens), but can be seen in gouramis (Osphronemidae family) as well.

Red Betta Fish

Bubble nests are made up of many microbubbles on the surface of the water, usually attached to aquarium plants, aquarium glass, or other equipment. These nests can have a foamy appearance.

It is often said that betta fish only make bubble nests when they’re perfectly happy in their environment. While this is largely true, bubble nests don’t always indicate that your fish is thriving. If your fish is creating bubble nests more than usual, make sure to check for poor water quality, as it might be a sign of stress.

The male betta fish typically maintain bubble nests for several days; some hobbyists have noted a bubble nest lasting more than a week. Eventually, the bubbles will dissipate, even quicker if they’re near areas of water flow.

8. Pearling

Another good reason why you might have bubbles in your fish tank is due to a sought-after phenomenon called pearling. This is the visualization of aquarium plants releasing oxygen into the water column; the oxygen produced is released faster than it can dissolve into the water. This is regarded as a sign of a healthy tank with rapid aquarium plant growth.

Pearling can result in bubbles covering the plant or floating to the surface of the water.

Do They Hurt Your Aquarium?

In general, air bubbles aren’t good or bad. There are many reasons for them to occur, with some reasons being neutral while others being good or bad. Small bubbles may be present in new fish tanks but they can also appear in well-established ones that have good a filtration system or that have regular water changes.

At the same time, foam in your fish tank can either be a sign of recent medication use and bad water parameters or a healthy betta tank with pearling. If you aren’t expecting air bubbles to be present in your aquarium, then it’s worth questioning.

9. Lookalikes

It’s pretty easy to identify air bubbles in a fish tank, but there are one saltwater pest algae that you need to keep an eye out for bubble algae (Valonia ventricosa). This presents small, green jewel-like bubbles that cover the surface of rocks, corals, and equipment. These bubbles can even get stuck in the intake of a powerhead or aquarium filter.

Newly-formed bubbles can have a more transparent appearance than older ones, making it confusing to realize they’re a type of algae. Some hobbyists like the appearance of bubble algae, but most try to eliminate it with regular maintenance as well as chemical and biological intervention.

How To Get Rid Of These In The Aquarium

Like anything in the aquarium hobby, to fix bubbles from appearing in your fish tank, you need to understand the root of the problem. Once that’s been discovered, small and large bubbles can be eliminated.

1. Preventing Them In A New Aquarium

There’s no reason to get upset over bubbles appearing in a new fish tank, but some hobbyists want to skip the waiting. There are a few ways to keep these bubbles out:

  1. Thoroughly rinse and soak all substrate, decorations, aquarium equipment, and filter media before use.
  2. Fill the aquarium with warm or hot water to lessen the amount of oxygen that enters the aquarium.
  3. Perform water changes to remove any foam bubbles that may appear on the water’s surface.
  4. Use an algae scrubber to wipe away any bubbles that form on the aquarium glass.

2. Decreasing Due To Air Stones And Filtration

Most hobbyists want to increase the amount of available oxygen in their fish tanks, just not in the form of microbubbles. While surface agitation is good, there are a few ways to prevent too many bubbles from entering your water column.

  1. Make sure equipment is securely installed. Connections and joints within the equipment should be fully submerged to prevent air from being introduced.
  2. Keep the air stone away from the filter. Bubbles can get sucked up and returned via the aquarium filter, creating additional bubbles.

3. Increasing Oxygen And Dosing Medications

Bubbles should be the least concern when dealing with dosing medications, but we understand that you want comfortable conditions for a sick fish.

The best way to stop thick bubbles from forming in a medicated fish tank is by increasing water surface agitation. This will introduce some bubbles on its own but should help break up the viscosity caused by the medications. Increased oxygen and carbon dioxide exchange will also help combat lowered oxygen levels due to treatment.

4. Removing An Oily Surface Layer

Natural oils are to be expected in both freshwater and saltwater fish tanks. These can be removed through improved water surface agitation, manual removal, or physical removal through something like a protein skimmer.

If your oily surface layer is due to a type of chemical, then there is more reason to be concerned. By the time these bubbles form, it’s usually too late for fish and invertebrates. However, a large water change can help save the remaining inhabitants.

In the future, steer clear of traditional cleaning products in and around your fish tank. Instead, use hot water and vinegar to clean what you need to.

5. Improving Water Quality

Improving water quality and reaching more ideal water parameters is a long game. It takes time and patience, and the road to a healthy ecosystem isn’t linear.

That being said, each fish tank is unique in how it runs. This means that the water parameters that work for one tank might not work for the next. However, no tank runs well with poor water quality.

Here are a few ways to improve the overall health of your aquarium:

  1. Use good source water. Source water should be within the ideal parameters needed for your fish tank or a blank slate; many saltwater keepers use RO/DI water that is completely customizable for what their tank requires.
  2. Perform regular tank maintenance. The importance of aquarium maintenance cannot be overstated. Vacuuming the substrate, introducing fresh water, and rinsing filter media can easily keep waste down and parameters where you want them to be.
  3. Take regular water tests. As you understand your fish tank more, you won’t need to do water tests as often. However, in the beginning, stages, and future problems, you want to know how your tank operates across days. This will identify the problem and stop it from reoccurring in the future.
  4. Check on your fish tank daily. The best way to track your fish tank progress is by checking on it daily. Most problems happen over time and not overnight (though things can go south very quickly!). Be there to see it as it happens and stop it before it gets out of hand.

6. Keeping Your Betta Fish Busy

There is some discussion as to how to ‘treat’ bubble nests. Betta fish work hard on their nests and can get stressed when they’re prematurely disturbed or destroyed.

What Is A Bubble Nest

At the same time, bubble nests are a great form of enrichment for betta fish. By destroying your betta fish’s nest by removing it or breaking it up, you are giving your fish something to do. Still, this can stress out your fish and cause a change in their demeanor.

7. Reduce Pearling

In general, pearling from aquarium plants is never a bad thing; it’s a highly desirable effect that many hobbyists dream of! But if you don’t like the look of it, then there is an easy way to fix it.

The best way to deal with aquatic plant pearling is by increasing water flow. This will dislodge and disperse any bubbles that form and rise. Be careful not to push your aquarium plants over with too much water flow, though.

Final Thoughts

Microbubbles can make a fish tank look unkempt and dirty. On the contrary, tiny bubbles are usually a good sign or the result of something else in the aquarium! Sometimes, bubbles are a sign that something is wrong in the aquarium, so any first or unexpected appearance of them should be taken into consideration.

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