When you suddenly notice your pet fish is gasping due to shorter of breath in the water, your first diagnosis may appear as something wrong with your fish. But that’s not always the case. Sometimes low oxygen in the water can cause your fish to labor breath.

The simple way to create oxygen in the water is to create a motion like a wave. That will help the CO2 to dissipate and dissolve more oxygen. Air pumping, pouring water from the top, and rapid water changing are some of the solutions to increase oxygen.

If you are a professional aquarist or just a beginner, you must know the importance of balanced dissolved oxygen levels in the water parameters for the safety of fish. Here, I am to tell you all there is to know about increasing oxygen in tanks.

Signs Your Tank Is Lower In Oxygen

Unfortunately, there are no alarms on the tank that can indicate oxygen deficiency. So, you have to manually detect the deficiency from the movement and activity of your fish. There are a few symptoms that can indicate a lower level of oxygen in the tank. Let’s see the signs.

Fishes Gasping

Generally, the gills of a fish move very gently and in a consistent manner. But when there is not enough oxygen in the water, the fishes have a hard time breathing. They usually gasp like they are having a problem inhaling and exhaling. Their gills movement will be incoherent and inconsistent.

Coming On The Surface

Fish generally prefer to swim and thrive on the bottom layer of a tank as they are more comfortable on the bottom where the water parameter is just correct. However, when there is a shortage of oxygen in the water, fish generally comes on the top of the surface to catch extra oxygen from the air or the top water level.

Lethargic Behavior

Aquarium fishes are generally very energetic and playful in nature. They love to swim around on the bottom layer of the tank. But when there is not enough oxygen, their playful nature vanishes due to a lack of energy and a shortage of breath. If you notice them, you can see they just lay on the side of their body without hardly moving.

Lack Of Appetite

Another sign of oxygen shortage is when fishes show apathy toward food or their ration. The lack of oxygen creates a very uncomfortable ambiance around the tank. It impacts the overall mood of the fish, which leads to a lack of appetite. Since the fish don’t feel very healthy due to the shortage of oxygen, you can notice they hardly touch their food.

How Much Oxygen Does Fish Needs?

The ideal oxygen level varies from species to species, but in general, fish living in the aquarium requires 5 to 6 PPT of dissolved oxygen to survive and thrive. The aquarium water needs to have 80-110% oxygen saturation to create a balanced oxygen level. If the oxygen level drops to three PPTs or lower, you can be sure that the fishes living in the aquarium are at great risk.

‘The more, the better’ theory does not apply when it comes to the oxygen level of the aquarium. Overburden of oxygen in the water can cause supersaturation which may create gas bubble disease in fish’s bodies. The bubble starts forming on the fish’s outer layer, such as the gills, fins, and scales. Eventually, such bubbles reach out to the hearts of the fish, which can put your fish on death row.

Why Does Oxygen Lessen?

Before putting fish in the tank, you probably have performed the cycling and tested the oxygen level to determine whether it is balanced or not. You may probably think it will remain the same since the oxygen was balanced in the beginning. Well, bad news for you. The oxygen level in the water can reduce significantly as time passes. So, let’s see why the oxygen lowers in tanks.


The most common reason for a shortage of oxygen in tanks is putting an excessive number of fish in the tank, or the size of the tank can’t accommodate the number of fish you have. Generally, for one inch of fish, you need to reserve two or three gallons of water. So, for example, for a pair of clownfish, you need at least 20 gallons of water for a balanced oxygen level.

Stagnant Water

Water in the aquarium has no way to flow or move around like an ocean or river. Such a stagnant situation gradually lessens the dissolved oxygen level in the water. Stuck water can’t participate in the chemical reactions occurring in the tank and hence, can’t break the oxygen particles or dissipate carbon dioxide.

Water Temperature High

High temperatures of water are unable to produce oxygen compared to cooler water temperatures. High temperatures can’t hold back oxygen in the tank as temperature initiates reactions, and oxygen, in the form of bubble air, disappears from the tank. For an ideal aquarium, 65-73° Fahrenheit is the perfect temperature for the water and the fish.

Live Plants But Low Lighting

You probably are wondering what’s wrong with live plants. They provide oxygen, right? Yes, they do. But if your tank has poor light settings, your live plants are unable to perform photosynthesis. The foremost starting point of photosynthesis is the presence of enough lighting to initiate the cycle. Without proper lighting, your plants are just inhaling oxygen without giving anything in return.

Unclean Tank

A dirty tank is a party house for unwanted bacteria and fungus. Bacteria utilize lots of oxygen to activate and multiply, causing a deficiency of oxygen in the water. Fish waste, rotten food, and algae overgrowth produce nitrates and bacteria, which by chemical reactions, use oxygen to break and create more dirt.

Chemicals And Medications

No matter how organic you want your tank to be, sometimes you need to add chemicals and medications to save your fish or the ambiance surrounding the tank. But those chemicals and medications can have side effects and lower the oxygen level in the tank.

Instant Ways To Increase Oxygen In Tanks

Once you have diagnosed the shortage of oxygen issue in the tank, you need to act immediately to restore the lost oxygen and increase the level of dissolved oxygen. For you, you do not have the luxury to perform long-term goals to increase oxygen in your tank instead. You need to find solutions that will level up the oxygen in the tank immediately. Luckily, we have some instant ways you can use to increase the oxygen level.

Pour Water From High Level

Remember we talked about how stagnant water deters the regeneration of oxygen due to lack of motion? Pouring water from a height will create a motion or a wave into the tank, which will oxygenize your tank in the fastest way possible. It is also the simplest way.

Take a clean jar or container and fill the container or jar with aquarium water. Take the lead of the aquarium and stand on a chair. Now gently and slowly pour the water from the top. Perform this cycle for a few minutes and observe the reaction of your fish and its gill movement.

Rapid Water Change

Frequent water change is a very sustainable way to ensure a balanced water parameter level in an aquarium. When your tank is in dire need of oxygen, the power of water changes again pops into your mind. Even performing a 50% water change will increase the oxygen level significantly within a short period of time.

The new water will have more oxygen that can combine with the aquarium water. it will be best if the new water can match the water parameters of your tank. However, since it is an emergency solution increasing the oxygen level in the tank should be the priority.

Manually Stir The Water

This is the easiest way to create oxygen in the tank. With the wooden spoon or long scale, stir the water gently and in a clockwise motion. Be very careful while using the technique because the spoon or scale can knock down the fish or push over the decoration. This is a safety measure for an immediate solution to oxygenize the water.

Cool Down The Heated Water

If the temperature in the water of the tank is elevated for some reason, the first step is to cool down the water. As we have seen, high temperature causes a shortage of oxygen in the water. You can either use ice chips or a fan to gradually take down the extra heat.

If you use ice chips, place them in a Ziploc bag so that melted ice does not incorporate with the aquarium water because that may change the tank’s water parameters. If you use a fan, please them on the top of the tank while taking the lid off. It will create ripples on the surface and cool down the extra temperature. Make sure to use a temperature sensor to read the correct temperature.

Use Air Pump

An air pump is a digital device that creates motion in the water of the tank by making bubbles. If you use a battery-charged air pump, you can use the product to oxygenize the tank even when there is a power outage. This is one of the fastest ways to increase the oxygen level in the tank.

Long-Term Solutions To Increase Oxygen

Instant remedies for the shortage of oxygen problem can save your fish for a brief moment, but it is better to level up your oxygen level so that you never have to face the oxygen reduction problem again. Instead of a cure, you must aim for prevention. So, Let’s see what long-term methods you can apply to increase oxygen.

HOB Filter

HOB stands for the hang-on-back filter, which is a type of water filter for your aquarium. It penetrates a portion of the water, clarifies them into its system, and releases it back into the aquarium. Using a HOB filter comes with many benefits.

Firstly, the taking in and giving back of the filter creates turbulence in the water to generate more oxygen into the tank. Also, the filter eliminates germs and nitrates without dilapidating the water parameters. It maintains the water quality and discharges fresh water into the tank. If you have a small to medium tank, you can install such filters to balance the oxygen level.

Fountain Head

Fountain heads can work as a mechanism to always keep the oxygen level in check and as a scenic decoration piece of your tank. It creates motion in the water and causes agitation on the surface. But if you are to install this fountainhead, make sure to manually purchase the device compatible with your tank. Water droplets can be an issue if you opt for this option.

Lily Pipes

Lily pipes are basically crystal glass pipes with one narrow part on the outer part and a wider, lily-shaped arc dunk inside the tank. This glass pipe is aesthetically pleasing looking and works wonder to increase the oxygen level inside the tank by creating aeration pressure from the outside to the inside. Just make sure to purchase one so that your fish is big enough not to get inside the pipes.

Swimmers At Different Levels

If you have a community tank filled with different types of aquarium fish, fill the tank with fish that swim in different portions of the tank. That way, you can avoid overcrowding and accommodate your tank to the fullest. Fast swimmers and schooling swimmers can create ripples in the water with their movement to increase the oxygen level.

Final Words

Just because fish is aquatic doesn’t mean they can’t ever be short of oxygen. Even with an abundance of water, your fish can suffocate due to a lack of oxygen. Once you have observed and diagnosed the problem, do not play for time to take action to restore and increase the oxygen level.

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