How to Set Up an Aquarium CO2 System the Easy Way

In order to help beginners with planted tanks, we recommend that they start with simple, slow-growing plants that require 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. Aquarists have tried many techniques and types of equipment to inject CO2 gas in water. Aquarium Co-Op has tried many and created this guide to help you choose the most reliable and simple method.

Is CO2 able to eliminate algae problems? A healthy plant tank must have three components balanced – light, fertilizer, carbon dioxide. CO2 is only one of the essential nutrients plants require to grow. Many people start with too much light and fertilizer. Therefore, adding CO2 can help balance your aquarium. Algae can develop if there is too much fertilizer or high lighting in a tank.

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). The recipe will not work if you use 5x the amount flour, and then only add 5x chocolate chips (e.g.. CO2). This will create a bad cookie (e.g.. algae growth).

Does every aquarium plant require CO2 injection? All aquatic plants use CO2 for their basic building blocks. While some types, such as cryptocoryne plants, don’t need extra CO2, other plants, like scarlet temple might benefit but don’t necessarily require it. Blyxa japonica (dwarf hairgrass), dwarf baby tear and similar carpeting plants are a third group that has higher needs and must be supplied with CO2 in order to have the best chance of success.

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. Gather the required equipment and tools to get you started.

1. Aquarium Co-Op CO2 regulating device What is a regulator and how does it work? How can you control the amount of gas that exits the tank’s CO2 cylinder and into the aquarium? How does a single-stage regulator differ from a dual-stage regulator. A single regulator reduces the gas pressure of the cylinder in one stage, while a double-stage regulates the pressure in two. This ensures that the CO2 flows more reliably and is less volatile. Two-stage regulators are also better at preventing “end-of tank dumps,” where a CO2 cylinder that is nearly empty may leak its remaining gas in one step. Is it better to use a DIY or pressurized CO2? We’ve tested many DIY systems that contain yeast and citric acid. However, they are less stable than a pressurized CO2 using a regulator/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. Additionally, the process is slower because of the low pressure and temperature. We can set it up once, and it will run for one- to three years before we have to refill it.

1. Aquarium Co-Op manifold add-ons – You can add up to five additional manifold blocks to your regulator to expand the system or run CO2 to multiple tanks.

1. CO2 tank – A CO2 paintball regulator. They can be used with standard cylinder tanks having the male thread CGA320. Where do I get a CO2 Cylinder? We prefer to buy ours at local home brewing supply shops and welding supply shops. Usually, they also offer CO2 refill services if you bring back your cylinder when it’s empty. Which size CO2 cylinder should you get? For high-tech planted aquariums that use high levels of CO2, it is recommended to get the largest size cylinder possible. This will allow you to not need to refill it as often. However, for the average customer, we often suggest a 2.5-5 lb. A 5 lb. cylinder is recommended for aquariums up to 20 gallon. For 25- to 40 gallon aquariums, a 10 lb. cylinder for aquariums up to 55-gallon. Scale the cylinder to fit five or six aquariums.

1. What is the difference between airline tubing and CO2 tubing? We use Aquarium Co.Op’s flexible black PVC tubing on all our aquariums. There has been no perceptible CO2 loss. Our experience shows that special CO2 tubing costs more, is harder to bend, and is not as easily available.

1. Regular check valve or stainless-steel check valve (optional). Do I require a CO2 regulator? Check valves prevent water from flowing out of your aquarium and pouring onto the regulator. The Aquarium Co-Op regulator includes a built-in bubble counter. You can however add a second to make sure it is working properly. 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. For greater durability, we also offer a stainlesssteel version of the CO2 check valves.

1. CO2 diffuser What kind of CO2 diffuser do I need? Anything that can operate at around 40-50 psi is fine. How can I clean a blocked CO2 diffuser? Algae buildup must be removed from the diffusers. Different materials can make diffusers, so follow the manufacturer’s cleaning instructions. 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. You don’t have to refill your bubble counter because the water will evaporate. Mineral oil can be substituted.

An electrical outlet timer Adjustable wrench with at least 1.25-inch width 2. Scissors 3. Spray bottle with water and a few drops of Dawn dish soap

How to Install a CO2 system

Once you have the necessary equipment, we recommend that you read our detailed manual and watch our video tutorial to learn how to use it. This diagram shows the connections between all parts of the CO2 system.

The regulator (B), attaches to the CO2 cylinder A. The regulator (B) can have optional manifold blocks added. – 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 the diffuser D, which is found at the aquarium’s bottom. The optional check valve, (E), is installed along with the airline tubing at 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 (H), which plugs into either a wall outlet, or power strip.

What if CO2 bubbles emitted from the diffuser get into the aquarium’s water surface? This is normal. Your aquarium should have your diffuser placed at the lowest possible level. 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.

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. Drop checkers are not used to achieve the ideal CO2 concentration, as we prefer to let the plants and nature tell us when they’re happy.

Photosynthesis is when plants produce oxygen (O2) and glucose as byproducts of photosynthesis during the day.

If plants have enough light, carbon dioxide, and oxygen, they can produce sufficient oxygen to saturate water. You can easily see tiny bubbles coming from their leaves. In our warehouse, we dial the CO2 level on our plant-holding aquariums until we consistently see this “pearling” effect. Plants are living things and it takes around 24 hours for any CO2 adjustment to have an effect. We like to wait three days before we make the next change.

When the water is saturated in oxygen, aquatic plants produce visible bubbles.

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. To optimize CO2 use, set the regulator’s timer so that it turns on about 1-2 hours before the aquarium light comes on. The regulator will then turn off approximately 1 hour before the light goes out. If you have only one timer, you could use it with a power strip to turn the regulator and light on at the same moment.

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. Hobbyists may try to reduce surface agitation in order to limit gas exchange and CO2 escape from 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.

We wish you every success with your pressurized CO2 regulator and we hope you have a lot of fun exploring the worlds of high tech plants. You can find more information about our CO2 regulator on the product page. There is a demo video and a manual.