CO2 And Aquarium Plants – Everything You Need To Know

CO2 And Aquarium Plants – Aquariums are a beautiful addition to any home with their calming and mesmerizing water and fish. But how can you make your aquarium even more appealing? Why not try adding some aquatic plants!

These plants will give your aquarium a great look, as well as provide cover for fish and natural habitats for other small creatures. In this post, we’ll discuss the importance of CO2 in an aquarium, what it does for photosynthesis, and which methods of providing CO2 work best.

We’ll also explore what equipment is required to inject CO2 into the tank, why a check valve is important and lots more.


CO2 And Aquarium Plants

Why Is CO2 Important For Plants In An Aquarium?

CO2 is a molecule that aquarium plants need to create sugars and oxygen. This gas comes from the fish respiration, as well as plant transpiration. Fish use their gills to take in the oxygen and give out the CO2.

The excess CO2 can cause harm to the tank eco system and affect the pH because carbonic acid gets formed in the water. However, the plants take in this CO2 and let out oxygen instead and this in turn helps the fish.


Given this, people may argue that you do not need to add CO2.. But, you need to understand that several factors such as the number of fish, the number of plants etc play a role in quantity of CO2.

Also, an aquarium cannot match nature in terms of providing all that your plants need to grow fully in terms of vibrancy and lushness. In aquarium language these are called color intensity and carpet development respectively.

It is very difficult to achieve the adequate level of CO2 by balancing everything in your tank. To assert this, you can simply test the CO2 level in your tank.

If you have achieved a perfect dark green without CO2, then it’s either a miracle or you are a pro. If not, you need to supplement the CO2 in your tank for optimum benefits.

Pro Tip: Remember, a yellowish green tint is not what you need. Here is a color chart to help.

CO2 And Aquarium Plants. Ideal CO2 Color to be achieved

Let us see what exactly CO2 does for plants in an aquarium. CO2 acts like a fertilizer for plants, by providing them nutrients they need to grow healthy and fast. This is more so when the lighting is low in your tank.

Mainly, it is an important factor in the process of photosynthesis performed by the plants in your aquarium. During photosynthesis the plants use the CO2 to get oxygen and sugar which is vital for their growth.

During the process of respiration in plants, the sunlight is used to transform CO2 and water into glucose/sugar molecules. This helps in the growth of the plant.

What Are The Symptoms In Plants When There Is Less CO2?

Low co² levels affect aquarium plants in a number of ways. If there is low CO2, it’s likely that the aquarium owner will notice slower growth rates and reduced green coloration on their plant leaves.

In addition to this, some species might even die – most often due to lack of light penetration from increasing amounts of algae growth! Low CO2 also reduces photosynthesis efficiency by limiting CO2 transport into chloroplasts through diffusion across the cell wall.


This means that when your CO2 drops too much, you can expect problems with nutrient absorption keep happening at a faster rate than usual!

A further effect relates to how quickly these effects happen: if your CO2 level is dropping slowly or gradually over time, your aquarium plants will be impacted more slowly.

Low CO2 Symptoms
Low Co2 symptoms

Does CO2 Help Fish?

Now let us look at how fish benefit from CO2. When the plants grow well, they become a good place for the fish to settle, hide and breed too. If you have a carpet, it is a great place to explore for the fish. This is referred to as ‘valuable cover habitat’.  

There is also an increase of microbes for the fish to feed on. These microbes are prone to grow when the plants are healthy. Another thing that happens is that the plants help keep the nitrate and phosphate levels low and this means a good pH. So that’s a great thing too!


What Are The Methods Of Providing CO2 In Aquariums? Is Injecting The Best Way?

There are many ways to provide CO2 for your aquarium plants –

Special tablets into water called pressurized carbon dioxide (pCO) are available with aquarium shops. These tablets allow the release of continuous bubbles into your fish tank ensuring constant level of oxygen and nutrients provided for photosynthesis process.

That’s why most aquarists would recommend this method.


There is also another opinion out there suggesting using good old yeast instead. This involves using yeast, sugar and baking soda to create your DIY CO2along with a DIY CO2supply kit.

This however, would require lot of effort and time from your side. If you are willing to do it, its not a bad idea.

The other method is injecting CO2. This method can be used both for planted and non-planted aquariums.

Methods of Adding CO2

What Is The Equipment Required For Injecting CO2?

There is a long list of items necessary to inject CO2 into your fish tank. However, this is only a one-time setup affair.

We start with the CO2 bottle which actually contains the CO2. These bottles are available in various sizes. Make sure you pick the right one based on the size of your tank.

You then have the regulator which ensures that the pressure is adjusted to a useable pressure. This is because the bottle has CO2 which is of much higher pressure than required.


You then have the Solenoid. The solenoid performs the function of stopping the CO2 flow during the times when the plants do not indulge in photosynthesis. This is attached to a timer.

Alongside, the bubble counter tells you how much CO2 is entering your tank per second.

Then there is the diffuser.  This is the only part that goes inside the tank. The CO2 is made to pass through a medium which is porous so that the CO2 is converted to bubbles while entering the tank making absorption easier.

A tube connects the diffuser and the regulator.

Pro Tip: Always check your tubes regularly and try to buy tubes which will not support leakage. They are called CO2 resistant tubes.

A drop Checker helps you know if the CO2 is adequate or in excess. This is actually very important.

Pro Tip: Remember CO2 can lead to a lower pH level and you need to monitor your pH levels regularly.

CO2 equipment

Why Is A Check Valve Important?

A check valve is used to prevent water back flow when injecting CO₂ into your aquarium. So it’s essential if you want to maintain the equipment!

The best option would be having two check valves – one right before solenoid valve and second between regulator and diffuser in case anything goes wrong with either of these items.

You can also add ammonia remover in this line after the second check valve to ensure water safety if you have any issues with CO2.

What Are The Benefits Of CO2 Injection?

There are lots of reasons why people would recommend injecting C02 into your planted tank instead using pressurized carbon dioxide tablets or yeast method.

First and most obvious one: it’s much easier, faster and cheaper way! Once you set it up, (a onetime affair), it is then just a matter of replacing the bottles or refilling the bottle. It’s possible to add more co² when needed and decrease it in case there is too much algae growth in your aquarium. Also, it is safer because the equipment is manufactured to precision. This increases the efficiency and thus can make it cost effective. The injection also allows the stopping of supply at night through the solenoid timer. Overall a reliable system.


The last but not least: you can easily adjust the level of oxygen, nutrients and CO2 into your fish tank providing perfect environment for healthy aquatic plants!

Just remember that injecting gas or yeast fermentation might seem like a cheaper option but proper maintenance will cost you some money as well so keep this in mind before making any decisions about adding carbon dioxide into your aquarium.

If you decide to go with the injectable method, make sure the substrate must be the one which provides maximum nutrition.

Benefits of Injecting

Pro Tip: If you only have a nano tank you might want to ask for paintball CO2.

What Else Should You Consider Before Using CO2?

Another thing you should consider is whether you want natural or artificial CO2 in your tank – some people are against using yeast due to carbon dioxide being a by-product of this fermentation process which might cause issues with PH levels dropping down below acceptable range but it’s more than possible that nothing will happen if everything gets done properly!


It depends on how well the whole system runs and what type of fish, plants and substrate do you have in aquarium. People who prefer injecting pressurized CO2 usually go for DIY solution since they feel like having something simple.

Pro Tip: bubbling CO2 into water through an air-stone might seem like a nice idea, however this is not a good idea and not advisable.  

What Are The Disadvantages Of Adding CO2 To Your Tank?

CO2 can cause pH imbalances. This can wipe your tank out. So, one has to be cautious while calculating the CO2. An excess of CO2 in the tank can cause the oxygen levels to go down and this will turn cause your fish to start gasping for oxygen.

CO2 system can be noisy and disturbing. The expenditure is also a recurring one in terms of CO2 bottles. However, if you calculate the cost per day, you might find it cheap. Take the help of your local aquarium store to calculate. This is because the cost of the CO2 bottle has to be taken into account.  


Also, knowledge about the working of the CO2 injection system and the equipment is important. Any fault in the equipment can result in harm to the fish. Also, availability of the CO2 bottles has to be kept in mind.

In comparison the DIY CO2 systems can have leakage and failure of the mechanism. Another thing that can happen is the failure to produce the CO2. This can cause further harmful reactions and injection of chemicals into your tank.

Further, the bubbles per second may not be efficient. There can be a case of CO2 poisoning.


Pro Tip: If you do decide to use CO2, then injecting CO2 is better with a back up system in place. Such as a small CO2 bottle or ordering CO2 in advance.

Wrapping Up:-

CO2 is very essential for aquarium plants. The plants tend to be more colorful and lush. CO2 is mainly added in three ways. Through tablets, yeast and injection. Among the three, injection is the most reliable method upon logical analysis. Everything has its pro’s and con’s. When you weigh them, your answer is easy.

Is CO2 Alone Sufficient For Good Plant Growth?

No CO2 alone is not sufficient for plant growth. One important nutrient that is required for plants in an aquarium is nitrogen. Nitrogen promotes healthy growth and lush green leaves.

Unless you have a pressurized CO² system, your aquatic friends probably won’t get enough of this essential nutrient from the water alone, so it’s likely they’ll need some help from supplemental fertilizers. Another essential nutrient that is required for plants in an aquarium is iron.

Iron helps assist with photosynthesis and keeps plant cells alive by transporting oxygen throughout them which basically prevents cell death before its time. If there is no sufficient iron available then brown spots can start to form on leaves. This apart they need phosphorous, potassium and magnesium too.

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