How to Set Up a CO2 System for Planted Aquariums the Easy Way (2023)

When it comes to planted tanks, we always encourage beginners to start with easy, slow-growing plants that only need low lighting and an all-in-one fertilizer. However, certain plants are a little more difficult to grow underwater and may require high lighting and extra carbon dioxide (CO2) beyond what is naturally provided in the air. When it comes to injecting CO2 gas into water, aquarists have tried all kinds of techniques, types of equipment, schedules, and dosage amounts to put together their own custom DIY systems. At Aquarium Co-Op, we have experimented with many of them and put together this basic guide to explain our favorite method that is reliable and easy to use.

Does CO2 get rid of algae? It’s a common belief that CO2 automatically fixes algae problems, but this is not true. A healthy planted tank must have three components in balance — lighting, fertilizer, and carbon dioxide. CO2 is just one of the primary nutrients that plants need to grow. Many beginners use too much light and fertilizer, so adding CO2 can help balance the aquarium. However, if a tank has high lighting and CO2 injection but, for example, too little fertilizer, then algae will appear because of the imbalance.

Let’s use a cookie recipe as an analogy. If you add 5x the usual amount of flour (e.g., fertilizer) to your dough, then you must also multiply the rest of the ingredients (e.g., lighting and CO2) by 5x, which will result in a bigger batch of cookies (e.g., greater plant growth). However, if you add 5x the amount of flour and then try to “balance” the recipe by only adding 5x the amount of chocolate chips (e.g., CO2), the rest of the ingredients are not in the correct ratio and will result in a bad cookie (e.g., algae growth).

Do all aquarium plants need CO2 injection? As mentioned before, all aquatic plants use CO2 as one of their basic building blocks. Some types like cryptocoryne plants do not need the extra CO2, while other plants like scarlet temple could benefit from it but don’t require it. A third category of plants — which includes Blyxa japonica, dwarf hairgrass, and dwarf baby tears and other similar carpeting plants — has higher demands and necessitates the use of CO2 for the best chances of success.

(Video) How To Set Up Aquarium Co2 System - The EASY Way

Materials for a CO2 System

In this guide, we are focusing on the installation of the CO2 system and not the lighting and fertilization components. To get started, gather the necessary equipment and tools:

How to Set Up a CO2 System for Planted Aquariums the Easy Way (1)

  1. Aquarium Co-Op CO2 regulator
    • What is a regulator? A regulator is a device that allows you to precisely control how much gas exits the CO2 cylinder tank and enters the aquarium water.
    • What is the difference between a single-stage vs. two-stage regulator? A single-stage regulator reduces the cylinder’s gas pressure in one step, whereas a two-stage regulator reduces the pressure in two steps, resulting in a more stable and reliable flow of CO2. A two-stage regulator also helps to prevent “end-of-tank dumps,” in which a nearly empty CO2 cylinder may dump out the rest of its gas in one go.
    • Should I use a DIY CO2 or pressurized CO2 system? We have tested many types of DIY systems using yeast, citric acid, and other mixtures, and while they may be cheaper, they are not as stable as a pressurized CO2 system using a regulator and cylinder. The DIY reactions often make lots of CO2 at the beginning and then decline over time, and the inconsistent amounts of CO2 can make it difficult to balance a planted tank. Furthermore, the pressure is not as high, temperature can affect the reaction, and the overall process is time-consuming to maintain. With a pressurized system, we just set it up once and let it run for one to three years before having to refill the cylinder.
  1. Aquarium Co-Op manifold block add-ons (optional)
    • With our regulator, you can install up to five extra manifold blocks add-ons to expand the system and run CO2 to multiple tanks.
  1. CO2 cylinder tank
    • Can I use a CO2 paintball cylinder? No, the Aquarium Co-Op regulator is not intended for use with paintball tanks. They work with standard cylinder tanks that have the male thread size CGA320.
    • Where can I buy a CO2 cylinder? We like to get ours from local home brewing supply stores and welding supply stores. Usually, they also offer CO2 refill services if you bring back your cylinder when it’s empty.
    • What size CO2 cylinder should I get? If you are running a high tech planted aquarium injected with high amounts of CO2, people recommend getting the largest size possible so you will not have to refill the cylinder as frequently. However, for the average customer, we often suggest a 2.5–5 lb. cylinder for 20-gallon aquariums or smaller, a 5 lb. cylinder for 25- to 40-gallon aquariums, and a 10 lb. cylinder for 55-gallon aquariums or larger. If you plan on using one regulator with five or six aquariums, then scale the cylinder size accordingly.
  1. Airline tubing or CO2 tubing
    • Do I need to use special CO2 proof tubing or CO2 resistant tubing? We use the Aquarium Co-Op airline tubing (i.e., a flexible, black tubing made from food-grade PVC) on all of our aquariums and have not detected any perceptible loss of CO2. In our experience, special CO2 tubing is more expensive, harder to bend, and not as readily available.
  1. Regular check valve or stainless steel check valve (optional)
    • Do I need a check valve for my CO2 system? Check valves are used to prevent water from flowing out of the aquarium and pouring all over the regulator when it is turned off. The bubble counter in the Aquarium Co-Op regulator comes with a built-in check valve, but you can install a second one as backup if desired. We have personally used the regular plastic check valves with CO2 systems at our fish store, warehouse, and homes, and they have not broken down. That being said, CO2 does degrade plastic after a very long time, so we also offer a stainless steel version for greater durability.
  1. CO2 diffuser
    • Which type of diffuser should I get? Any CO2 diffuser intended for aquariums that can operate at approximately 40–50 psi should be fine.
    • How do I clean a CO2 diffuser if it becomes clogged? Diffusers must be cleaned or replaced at some point because of algae buildup. Because diffusers can be made of different materials, follow the manufacturer’s cleaning instructions to use diluted bleach, vinegar, or other methods.
  1. Water or mineral oil
    • Regular tap water can be used to fill the bubble counter so that you can see the approximate rate at which CO2 is entering the aquarium. However, the water will evaporate over time, so mineral oil can be used instead so you never have to refill the bubble counter.
  1. Electrical outlet timer
  2. Adjustable wrench with at least 1.25-inch width
  3. Scissors
  4. Spray bottle with water and a few drops of Dawn dish soap

How to Install a CO2 System

Once you have all the equipment, we recommend you follow our detailed manual and video tutorialfor step-by-step instructions. To help you visualize the entire CO2 system, this high-level diagram shows how all the parts are connected:

How to Set Up a CO2 System for Planted Aquariums the Easy Way (2)

(Video) Beginner CO2 Setup Guide for Planted Aquariums | EP10 Planted Tank Overview

  • The regulator (B) screws onto the CO2 cylinder (A).
  • Optional manifold block add-ons can be added to the regulator (B).
  • The bubble counter (C) on the regulator is filled with liquid, and airline tubing is attached to the lid of the bubble counter.
  • The airline tubing connects to the diffuser (D), which is placed at the bottom of the aquarium.
  • The optional check valve (E) is installed in line with the airline tubing near the aquarium rim.
  • The regulator’s solenoid valve cable (F) is connected to the power adapter (G).
  • The power adapter (G) plugs into the electrical outlet timer (H), which plugs into a wall outlet or power strip.

Is it bad if the CO2 bubbles from the diffuser are reaching the water surface? No, this is normal. The key is to place your diffuser as low as possible in the aquarium. When the bubbles are released from the diffuser, they imperceptibly get smaller and smaller as they rise and the CO2 gas is being absorbed into the water.

How to Set Up a CO2 System for Planted Aquariums the Easy Way (3)

Place the diffuser at the base of the aquarium to give the CO2 bubbles a longer time to dissolve into the water.

How Much CO2 to Dose

In the manual, we recommend tuning the regulator to approximately 1 bubble per second (i.e., the rate of CO2 bubbles flowing through the bubble counter) because we would rather start with a lighter amount of CO2 to keep the fish safe. That being said, CO2 dosing amounts are different for every tank, and the bubble rate is not a perfect form of measurement since each aquarium has different plant and fish stocking levels. Also, we personally do not use drop checkers to chase the “perfect” amount of 30 ppm of CO2, but instead we let nature and the plants tell us when they are happy.

(Video) HOW TO: Make a long lasting DIY CO2 system - Low Budget CO2 System

When the plants photosynthesizing during the daytime, they consume carbon dioxide and produce oxygen (O2) and sugars as a byproduct. If the plants have enough light and carbon dioxide, they can produce so much oxygen that it saturates the water and you can visibly see small bubbles released from their leaves. In our warehouse, we dial the CO2 level on our plant-holding aquariums until we consistently see this “pearling” effect. Because plants are living things, it usually takes at least 24 hours after we adjust the CO2 to see any effect, so we like to wait three days before making the next change to the system.

How to Set Up a CO2 System for Planted Aquariums the Easy Way (4)

Aquatic plants “pearl” or visibly produce bubbles when the water is saturated with oxygen.

When should I turn on and off the CO2 in my aquarium? As mentioned before, plants use CO2 when there is light to photosynthesize. However, the process reverses at night and becomes the respiration cycle, in which plants consume oxygen and sugars and release CO2. Therefore, we want to shut off the CO2 regulator when the aquarium light is off. For more optimized CO2 usage, program the regulator’s timer to turn on 1–2 hours before the light comes on and turn off 1 hour before the light shuts off. (If you only have one timer, you can use the same timer with a power strip so that the light and regulator turn on and off at the same time.)


Is CO2 dangerous for aquarium fish? It can be harmful for animals in large enough quantities if (1) CO2 causes the water pH to drop too quickly or (2) people try to be so efficient with the CO2 that they end up cutting off the oxygen that fish need to breathe. In the latter case, some hobbyists try to minimize surface agitation so that less gas exchange occurs and less CO2 escapes the water. However, less gas exchange also means less oxygen will enter the water, which can cause your fish to struggle and gasp for air. Our recommendation is to increase both CO2 and O2 in the water by using an air stone (or other device that agitates the water surface) in conjunction with your pressurized CO2 system. Yes, you may have to increase your bubble rate a little to compensate for the slight loss of CO2, but having enough oxygen for your fish (and plants at night) is more important and can help lead to the pearling effect that is so desired by planted tank enthusiasts.

Best of luck with your new pressurized CO2 system and we hope you have fun exploring the world of high tech plants. For more information on our CO2 regulator, check out the product page for the official manual, demo video, and more.

Learn More



How to Set Up a CO2 System for Planted Aquariums the Easy Way? ›

A bit of CO2 (e.g. 3-5 mg per L) is better than nothing. Plants that are marked "Medium" require about 10-15 mg CO2 per L, but "Advanced" plants require 15-30 mg CO2 per L.

How much CO2 do I need for a planted aquarium? ›

A bit of CO2 (e.g. 3-5 mg per L) is better than nothing. Plants that are marked "Medium" require about 10-15 mg CO2 per L, but "Advanced" plants require 15-30 mg CO2 per L.

How do I connect my CO2 to my aquarium? ›

​Diffuser - a diffuser allows an effective method for CO2 to enter the aquarium. The CO2 is pushed through a porous medium that breaks down the gas into a fine mist of bubbles. These bubbles are then more easily absorbed by your aquarium water. Position your diffuser on the oposite side to your out-let flow.

How much faster do aquarium plants grow with CO2? ›

You can grow your aquatic plants in your aquascape 5-10 times faster by supplementing CO2. This is one benefit, but there are plenty more that come with using CO2 in a planted aquarium. Excited to find out?

What is the best way to add CO2 to a grow room? ›

Hanging carbon dioxide bags

Using Exhale CO2 bags is the easiest and cost-effective way to add CO2 to your grow room. No setup is required, just hang it above the growing space, because CO2 is heavier than air. It willcontinuously release CO2 24 hours a day forabout 6 months.

Is CO2 injection necessary for planted tank? ›

If you have very low light, then it is not necessarily necessary to inject CO2. However, if you have medium–high lighting and regular fertiliser dosing, injecting CO2 in your aquarium for optimal growth is highly recommended. So, in short, the more factors you give your plants to grow optimally, the better.

Can too much CO2 hurt aquarium plants? ›

Algae Overgrowth

Algae can quickly overgrow in a planted tank if there is too much CO2. This is because excess CO2 can provide an abundant food source for algae, which can cause it to grow out of control. Algae overgrowth can lead to unsightly green water and can also harm the plants in the tank.

How much CO2 does a plant need per day? ›

Plants during photosynthesis use carbon dioxide. Rate of consumption varies with crop, light intensity, temperature, stage of crop development and nutrient level. An average consumption level is estimated to be between 0.12–0.24 kg/hr/100 m2.

Can too much CO2 cause algae? ›

The good news is, YOU DO NOT have to experience algae in your planted aquarium. Algae normally appears when there is an imbalance in nutrients, CO2, oxygen and light. For example, too much light but too few nutrients and CO2 will cause algae. Poor distribution of CO2 and nutrients is also a common cause of algae.

How long do you leave CO2 in an aquarium? ›

For most of our tanks, lights and CO2 injection are turned on for a duration of 8 hours per day. For beginners afraid of algae, using a short light cycle such as 6 hours can be helpful. For stable, matured tanks, light duration can be pushed to 10hours+ without adverse effects.

Can you put too much CO2 in an aquarium? ›

However, high levels can be detrimental because carbon dioxide reduces the ability of a fish's blood to transport oxygen. Fish in water with high carbon dioxide concentrations (>10 12 mg/L for some fish species) can suffocate even if oxygen levels are high.

Should you run CO2 at night? ›

Growers can artificially increase the amount of atmospheric carbon dioxide (CO2) available to plants to improve growth and yield. But at night, plants do not uptake CO2 for photosynthesis. Maintaining artificially high levels of CO2 at night may, therefore, be wasteful.

Does CO2 make algae grow faster? ›

By introducing CO2 into the aquarium, plants can achieve healthy growth faster and therefore outcompete algae. When plants receive CO2, they produce oxygen as a byproduct of photosynthesis.

What time of day do plants absorb CO2? ›

During daylight hours, plants take in carbon dioxide and release oxygen through photosynthesis, and at night only about half that carbon is then released through respiration.

What is the cheapest way to generate CO2? ›

1. Slow-release CO2. This is by far the easiest and lowest cost method. You simply hang slow-release CO2 bags or bottles in your grow room.

How do I add CO2 to my aquarium naturally? ›

In fact, adding a few fish, shrimp, or snails is highly recommended because it will create a more natural ecosystem with higher CO2 generation. As previously mentioned, fish will exhale CO2, and the plants will turn these molecules into dissolved oxygen, thus creating a win-win situation for the tank.

Can you have too much CO2 in your grow room? ›

Adding CO2 is common and safe in an indoor grow room or greenhouse. Supplemental CO2 is useful for plants growth. However, a sealed grow room can trap dangerous levels of carbon dioxide that can lead to severe health effects such as dizziness, unconsciousness, or can even be fatal.

How often do CO2 tanks need hydro? ›

Hydrostatic (Hydro) Testing is a process where components such gas cylinders are tested for strength and leaks. Aluminum CO2 cylinders require testing every 5 years. At the time of testing, a date stamp will be imprinted into the cylinder near the top of the tank.

Will an air pump add CO2 to aquarium? ›

An aquarium air pump is a device that injects air into a tank's water. At the top of a tank, oxygen enters the water and carbon dioxide is released with the help of surface agitation.

Do fish provide enough CO2 for plants? ›

To answer the question of whether fish can produce enough co2 to sustain aquarium plants, we conclude that yes, they can. They can with a limited amount of low-light, slow-growing plants specifically chosen for a low-tech tank.

What are the signs of CO2 deficiency in aquarium plants? ›

There is no need for CO2 injection at night. The main symptoms of carbon deficiency are: (1) necrosis, (2) chlorosis, (3) stunted growth, and (4) twisted leaves. Necrosis is the death of plant tissues, turning it brown. Chlorosis is the yellowing of leaves as chlorophyll begins to die.

Do aquarium plants use CO2 at night? ›

However, plants can only do this during daylight hours when they undergo photosynthesis from your aquarium lighting. During the day, aquatic plants absorb CO2, producing O2, and during the night they absorb O2 and produce CO2.

How do you know if your plants are getting too much CO2? ›

High CO2 levels cause plants to thicken their leaves, which could worsen climate change effects, researchers say. Plant scientists have observed that when levels of carbon dioxide in the atmosphere rise, most plants do something unusual: They thicken their leaves.

What level of CO2 is best for plants? ›

The level of 1000 PPM CO2 is very close to the optimum level of CO2 required, given no other limiting factor, 1200 PPM, to allow a plant to photosynthesis at the maximum rate.

Is CO2 better for plants at night or day? ›

You are correct, plants do release carbon dioxide (CO2) at night, although they also release CO2 during the day. This is a part of the process of respiration! First though, you should know that during the day, when there is enough sunlight, plants undertake a process called photosynthesis.

What is the best CO2 for plants? ›

In an indoor space with normal fresh air ventilation, the CO2 concentration should be around 400 ppm. This leads to growth rates like what you would expect if you were growing your plants outdoors. Growers have achieved the best success with CO2 levels between 1,200ppm and 1,500ppm.

What kills green algae? ›

Chlorine is still one of the most effective killers of algae so doing a super-chlorination of 10-20 ppm of chlorine can go a long way towards wiping out the algae. Liquid chlorine is an ideal shock for algae because it is fast acting and does not add cyanuric acid (CYA) or calcium to the water.

What algae eats carbon dioxide? ›

Blue-green algae (cyanobacteria), green algae, red algae, and diatoms are commonly referred to as microalgae. These organisms have been used for capturing carbon dioxide and sequestration.

What algae uses the most CO2? ›

The reactor uses a specific strain of algae called chlorella vulgaris, which is claimed to soak up much more CO2 than any other plant.

Do air stones add CO2? ›

Air stones replenish CO2 via surface agitation

Air stones help add CO2 to tanks that have been depleted of it. CO2 is crucial for healthy plant growth. It is absorbed into a plant's chlorophyll and converted into glucose and used as energy for plant growth.

How much CO2 do I need for a 20 gallon tank? ›

However, for the average customer, we often suggest a 2.5–5 lb. cylinder for 20-gallon aquariums or smaller, a 5 lb. cylinder for 25- to 40-gallon aquariums, and a 10 lb. cylinder for 55-gallon aquariums or larger.

How long does a 5 gallon CO2 tank last? ›

For example, if your homebrewing equipment features corny kegs (5-gallon capacity), a small 2½-pound CO2 tank will dispense for about 7 to 11 kegs while a 10-pound CO2 tank can last up to 44 kegs.

Where do you put a CO2 atomizer? ›

​Diffusers should always be placed in the down wash of the water outflow current; bubbles should be fine enough to get pulled by the current downwards when they first exit the diffuser.

What is the best way to dissolve CO2 in a planted tank? ›

In order to boost the concentration of CO2 in a planted tank, CO2 injection is the best way. Here comes the importance of CO2 diffusers.

What temperature should CO2 tank be? ›

CO2 Tank Storage

CO2 tanks and cylinders should be stored in areas with a temperature less than 125F (51.7C). CO2 tanks and cylinders should always be connected to a reducing valve or regulator with a pressure safety valve.

Does CO2 help with algae? ›

CO2 never directly prevents algae from growing? It helps the plants so the plants can prevent the algae from growing. It is an indirect contributor, but one thing makes carbon dioxide one of the best algaecides. One of the effects of carbon dioxide injection in the tank is it turns the tank water slightly acidic.

Where should a CO2 burner be placed in a grow room? ›

CO2 Burners - best for grow rooms

These are housed in a metal box that is hung from the ceiling of the grow room above the canopy of the plants.

How to make a CO2 generator for a grow room? ›

A very basic Carbon Dioxide generator can be easily made with sugar, baking soda, and dry active yeast. Other methods include Dry Ice and baking soda/vinegar. Producing C02 with dry ice works to a very limited extent by simply allowing dry ice to melt in your grow room, it will boost the c02 levels.

How do you make a CO2 generator for plants? ›

To start, citric acid or vinegar is poured into bottle A, and a mixture of baking soda and water is poured in bottle B. The caps with tubing attached are the screwed onto the bottles. The needle valve is opened, and bottle A is squeezed slightly to inject Citric Acid in to bottle B. This starts the generating of CO2.

What do I need for a CO2 system? ›

Those being: A CO2 Cylinder, regulator, co2 proof tubing, check valve, bubble counter and lastly a diffuser.


1. Complete CO2 System Set Up with a DIFFUSER
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