CO2 System for Aquarium – A Definitive Guide

Is CO2 necessary for a planted aquarium?

Truly speaking CO2 injection is not necessary for a planted aquarium. However adding a CO2 system will definitely encourage plant growth and they will grow faster. When you have faster plant growth you’ll have an ecosystem that gets balanced faster because plants take care of the extra toxic gases such as nitrites and nitrates that may cause trouble for the fish.

Biologically we all know that plants consume CO2 and release Oxygen that fish can consume. On the other hand fish exhale some amount of CO2 as well. Gas exchange is happening at the top surface of the aquarium from where some carbon dioxide also comes into fish tank water. However CO2 mixed naturally in this manner is just about 3-5 PPM.

Apart from these, plants also consume toxic gases nitrites and nitrates that make the water safe for fish. In this way a beautiful ecosystem gets developed in the aquarium water that is beneficial for fish and at the same a time a planted tank looks much more visually pleasing to human eyes from outside.

When plants grow faster they provide extra surface area for the beneficial bacteria to grow and form colonies. These beneficial bacteria as well as plants themselves consume the toxic gas for their own growth making the fish tank water completely toxic free.

However excess plant growth has some disadvantages as well. A faster plant growth will require additional lighting above the tank because plants require light for photosynthesis. If this light source becomes excess then this can encourage algae growth in the tank. That’s why a balance must be maintained in the tank while introducing CO2 from outside.

It’s completely fine if you don’t introduce CO2 in your aquarium if you have live plants in them, but in that case you must follow the rules of aquarium maintenance by testing water frequently using a water testing kit so that toxic gases like ammonia, nitrates and nitrites don’t cross their limits.

Why is CO2 required in an aquarium?

CO2 is primarily required in an aquarium only if you have live plants. Live plants consume cO2 and release oxygen in the eater. Apart from CO2 plants also require natural light for photosynthesis. However CO2 will only encourage faster growth of the plants and is not always a necessity. Once you introduce CO2 plants will grow faster and if this happens you’ll also need frequent pruning of excess branches.

If you don’t introduce CO2 plants will consume it from the gases that get exchanges at the surface level of the water and grow with a normal speed. Plants also consume toxic gases like nitrates and nitrites in the water column making the water safe for fish.

Normally a tank without any system setup for CO2 injection will have 4 PPM of cO2 but that can be increased artificially up to 30PPM for faster growth of plants.

If plant growth is faster then there is always a better chance that plants will consume nitrates and nitrites faster.

How much co2 is needed for a planted aquarium?

The correct quantity of CO2 in an aquarium is 30 PPM. If CO2 is excess then these plants will not die nor will there be any damage to them, but fish will definitely suffer. This is because Carbon Dioxide is a toxic gas, it is what fish and other animals exhale while breathing. Plants consume CO2 and exhale oxygen.

That is why too much CO2 can harm your fish. You must have a proper system to measure Co2 in your aquarium to strike a proper balance between dissolved gases in water column.

How is CO2 introduced in an aquarium?

Pressurized CO2 can be introduced in the tank in the form of CO2 cylinders. Carbon dioxide is filled in these cylinders or bottles in with high pressure and that’s why care must be taken and should never be opened unless you have a regulator fixed to it at the top.

Carbon dioxide is highly toxic to humans and if a cylinder leaks in a room then this can cause death as well. You must strictly keep these away from kids to handle. Even excess CO2 in the aquarium water can kill fish because it will drastically reduce oxygen levels for the fish to breath.

Disposable CO2 cylinders – These come in the form of disposable cylinders that must be thrown when the gas runs out of them. They come with a single stage regulator built into it. The problem with these types of regulators is that at the end of the gas contents in the cylinder these regulators do not show indication that the gas cylinder is going to be empty and the cylinder dumps all the gas at once through the regulator into the tank which can be dangerous for fish. This is called as “End of Tank Dump”. You can get these on amazon.com for about $100 approximately

Refillable CO2 cylinders – This requires a Dual Stage Regulator. A dual stage regulator has an indication of the amount of gas pressure present in the cylinder as well as how much pressurized gas is being released into the tank.

Fire extinguisher CO2 Cylinders – The regular fire extinguisher cylinder can be used for aquariums with a dual stage regulator.

How much CO2 for planted aquarium is needed?

The satisfactory level of CO2 in an aquarium is about 30 PPM. Anything less than 30 PPM will not harm your plants because CO2 is not really a necessity if you have a planted tank in the first place. It’s just that plant growth will be slower if you have less CO2 in the tank.

The best way to measure CO2 is to install a “drop checker” which has a glass bulb filled with a solution which changes color when CO2 concentration levels change in the tank.

Is liquid CO2 good for aquarium plants?

Many fish keepers use liquid carbon dioxide use primarily to kill excess algae. One thing you must always remember is that whenever you add a chemical to your tank you must know what it does to not just to your plants but fish as well. We have already seen that CO2 in excess form is toxic to fish and must be used with extreme precautions.

Actually the base chemical in liquid CO2 products is “Glutaraldehyde”. Apart from growing aquatic plants faster this has a variety of different uses apart from aquariums such as

1. High level disinfectant
2. Preservative
3. Industrial water treatment
4. It is also used to remove warts from skin
5. It’s non corrosive

So why use liquid carbon in your tank?

It is used because it is cheaper than a pressurized cylinder system that requires a cylinder and a dual stage regulator with all other accessories.

How do you make homemade CO2?

The whole aquarium CO2 system can be costly which includes the cylinder, the dual stage regulator and other accessories such as tubing and the diffuser . The cylinder itself will cost you about $100 to $110 and add the extra cost of dual stage regulator to about $30 to $200 depending upon the features you buy.

Here is the procedure to make your own homemade CO2 system.

As you can see in the figure above, this system contains two plastic bottles and the chemical reaction (Fermentation)) in the Bottle A creates the CO2 that gets passed to Bottle B.

Bottle A = This is a 2 liter plastic bottle filled with a special solution. This bottle is 3/4 filled with water. The composition of this solution is a as follows

1. About 1.5 liters of water
2. 200 gms sugar
3. Add to this a solution made in another cup

The solution from other cup

1. Take a cup of lukewarm water
2. Add 3 teaspoons of “yeast powder” and stir.
3. Add this solution to Bottle A

Bottle B = This bottle is smaller than Bottle A (about half size). It contains normal water filled about 80%.

Just finish up the tubing as shown in the figure and you’ll see the diffuser release the CO2 after about 24 hours.

If you are just starting out then you can make Co2 system at home with cost of just $5 or less. But there are downsides to this such as

1. You can’t regulate the pressure of CO2 that’s getting in the tank
2. It runs for 24 hours continuously
3. You can’t detect when it will run out
4. You can’t increase or decrease it’s pressure if the quantity is too much or too less.

But the only advantage is it is very cheap than the professional systems. There is no harm in trying out this system if you are beginner and then shift to a professional one later.

What are Signs of too much CO2 in aquarium?

It is possible that you dump too much CO2 in the aquarium either by accident or by setting up the system incorrectly. The way to identify if there is too much CO2 in your aquarium is to observe fish behavior.

When there is too much CO2 in your aquarium fish will gasp for air (oxygen) and try to breathe from top of the water surface. CO2 is a toxic gas and is harmful for most fish in your tank. That is why it is necessary to measure and carefully control the amount of CO2 that goes in your tank on a regular basis.
Another way to find out if you have excess CO2 in your tank is to install a “Drop Checker” equipment.

This drop checker has a liquid in it which turns color depending upon the amount of CO2 in the fish tank water. If you see the color of the liquid in drop checker has turned “yellow” they it means there is too much CO2 in the water. The normal color of the liquid in the drop checker is blue.

How long should I run cO2 in aquarium?

The purpose of having CO2 in you tank is to encourage live plant growth. Apart from CO2 live plants also need lighting for photosynthesis and that’s why it’s better if you turn the CO2 supply one hour before the lights turn on. You can shut down supply of CO2, 1 hour before the lights turn off. This much quantity of CO2 is enough for most tanks.

The truth is there is no correct way to do this. It all depends on how many plants you have in the tank and how fast you need to grow them. If you encourage plant growth too fast you’ll see drop in toxic gases rapidly because plant will consume those fast. Faster plant growth will require more lighting hours and more nutrients to cover the extra plant growth. If you increase the number of hours of CO2 supply then you must keep measuring it’s levels using a “drop checker”.

One thing you must check is pH value of your aquarium water. Excess of Co2 lowers pH value of water which can be a red signal for fish health. Too much CO2 in the tank will make the fish to gasp for air at the top surface of the tank because it’s a toxic gas and excess quantity will affect fish health as well. If you find that the CO2 levels are too high you can always adjust levels using Dual Stage Regulator attached to the CO2 cylinder and check result again.

How to measure CO2 in aquarium water?

By now we know that too much of CO2 is not good for aquarium fish because it’s a toxic gas. It is what animals and fish too exhale from bodies. That is why introducing too much CO2 in aquarium water is always going to be trouble.

There are ways to measure CO2 in the water column so that we are always on safe side. The traditional method of measuring CO2 is using a pH/KH table.
The procedure is like this.

1. Collect 10 ml of aquarium water in a test tube and add 5 drops of solution from the pH/KH kit so that it’s color changes to orange. Tally this color with the available color chart to find value of the pH
2. Then collect 5 ml of aquarium water in another test tube and add drops of KH solution till the color of water changes to bluish.

Once these reading are with you tally the final result to a pH/KH table. You can find the pH/Kh table easily on the internet.

Using the pH/KH table you can easily identify whether CO2 is high or moderate in your tank. The reading you get is generally PPM (Parts Per Million). If you’re reading show a value of 30PPM or more then this is a sign of excess CO2 in your tank.

This method of measuring CO2 is actually very inaccurate because it requires you to visually tally colors of water from the test tube with the supported color chart visually which can be a little subjective.

The correct and accurate method to measure CO2 in the aquarium.

The correct way to measure Co2 is to use a device made of glass called as “drop checker”. This sits on the glass walls of the aquarium with one portion dipped inside the water and one portion outside of the tank.

This device has a small bulb at it’s end which has a solution. If the color of the solution is green then you can fairly say the CO2 levels are safe in the tank. The safe CO2 levels in the tank are up to 30 PPM. When you buy a drop checker device you must also buy the necessary solution that goes in the bulb of the glass bulb so that you get a kit with you to measure CO2. Once you install this device the drop checker will start changing the color in about 2 to 3 hours.

When the CO2 levels become excess then the color of the drop checker solution starts turning yellowish and this is when you must take necessary measures to reduce Co2 in the tank.

When the Co2 levels are lower, then the colors of the drop checker solution starts turning bluish which means you can increase the CO2 intake in the tank safely.

How to Lower excess CO2 in the tank?

To reduce excess Co2 in the tank you can do two things simultaneously.

1. Reduce CO2 pressure coming from the cylinder. You must have a dual stage regulator attached to the CO2 cylinder which makes the job a lot easier in this case.
2. You can increase oxygen intake in the water. To do this you can alter the air pump pressure by controlling the knob so that aquarium water surface gets agitated and more gas exchange happens at the surface level of the tank.

Can too much CO2 kill aquarium plants?

Excess of CO2 in aquarium will not kill plants but one thing to note here is that too much CO2 will reduce pH of fish tank water and this can be a trouble for fish. When CO2 becomes too much in your tank you will see fish gasping for air at the top surface of the tank because it’s a toxic gas.

There are ways to measure the amount of CO2 in water column so that you are always on the saferside of the chemistry part of the aquarium.

How do I know when to replace CO2 cylinder?

If you are using a refillable CO2 cylinder then to regulate the flow of pressurized CO2 you must attaché a “dual stage regulator” to the cylinder opening. This regulator comes with two gauges that show the remaining CO2 pressure inside the cylinder.

By looking at the reading on the gauge you can fairly find out when you must replace the cylinder. One gauge on the cylinder shows you available pressure in the cylinder and the other gauge will help you to adjust the outdoing pressure in PPM so that you don’t send excess CO2 in the fish tank.

Signs of low CO2 in planted aquarium

There are some signs that show there is less amount of CO2 in your aquarium. The easiest way is to install a device called as a “drop checker” on the glass walls of your tank. This device has a liquid filled in it’s glass bulb and when the color of this liquid becomes “bluish” you can fairly say that there is low Co2 in your aquarium.

Having low Co2 in your aquarium is not a big problem but excess of CO2 is definitely something that you must be aware of. CO2 is a toxic gas and excess of it will not kill you plants but will definitely harm your fish. Once CO2 becomes excess fish will gasp for air at the top surface of the tank. Excess of CO2 gas also reduces pH levels of aquarium water.